OF  THE 

university 

OF 
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NEW  TRUTHS 


IN 


OPHTHALMOLOGY, 


AS  DEVELOPED  BY 


G.  C.  SAVAGE,  M.D., 

Professor  of  Ophthalmology   in    the   Medical  Department   oj   the  Yanderbilt   University,   ex- 

President  Nashville  Academy  of  Medicine,  President   Tennessee  State  Medical 

Society,  Member  Eighth  International  Congress  of  Ophthalmology  . 


FIFTY- EIGHT  ILLUSTRATIONS. 


TIITRD  EDITION. 


Published  by  the  Author. 

Printed  at  tiif  Publishing  House  ok  hie  M.  E.  Church,  South, 

Nashville,  Tenn. 

1896. 


^o^^v^^c/ 


Entered,  according  to  Act  of  Congress,  in  the  year  1893, 

By  G.  C.  Savage, 
In  the  Office  of  the  Librarian  of  Congress,  at  Washington. 


S3 


opto:  . 

UBh. 


THE   AUTHOR   DEDICATES  THIS  LITTLE  VOLUME 

Go  tbe  dfcemorv?  of  S.  2).  Gross,  dfc.2>.,  iX.2>.,  B.C.X., 

WHOSE  ADVICE  GIVEN  HIM  WAS:    "  STUDY A  SPECIALTY ';  " 
AND 

Co  Oeorge  Z.  Stevens,  dfc.D., 

WHOSE  ORIGINAL  WORK  HAS  BEEN   OF   INCALCULABLE   VALUE  TO 

HIM   IN  HIS  SEARCH   AFTER   TRUTH,   AS   IT   PERTAINS  TO 

THE  SCIENCE  AND  PRACTICE  OF  OPHTHALMOLOGY, 

HIS  "  STUDIED  SPECIALTY." 


M675146 


Preface  to  the  First  Edition. 

In  presenting  this  little  volume  to  ophthalmologists  who  read,  the  author 
feels  that  he  is  doing  them  a  service  that  will  be  appreciated.  He  offers 
no  apology  for  publishing  what  he  believes  to  be  new  and  valuable  truths, 
after  having  demonstrated,  to  his  own  satisfaction,  their  practical  value. 
He  claims  that  the  truths  set  forth  in  Part  I.,  Chapters  I.,  II.,  and  V.  are  his 
by  right  of  discovery  and  development;  and  that  there  is  enough  new  in 
Chapters  III.,  IV.,  and  VI.  to  justify  their  being  placed  in  Part  I.  In  estab- 
lishing the  practical  value  of  what  is  taught  in  Part  I.,  the  author  is  in- 
debted to  Dr.  George  H.  Price  for  earnest  and  efficient  cooperation. 

Part  II.  is  given  as  an  expression  of  the  author's  views  on  the  two  long- 
studied  subjects  treated  therein. 

Part  III.  contains  brief  descriptions  of  five  operations  which  are  the  au- 
thor's either  by  device  or  modification. 

In  the  body  of  this  book,  the  author  has  mentioned  by  name  those  to 
whom  he  felt  speciallv  indebted  for  aid  while  "  weaving  his  webs  of  thought." 
It  only  remains  for  him  to  acknowledge  the  aid  rendered  him  by  his  brother, 
Prof.  G.  M.  Savage,  in  the  detection  and  correction  of  errors  in  both  copy 
and  proof;  and  to  thank  the  several  persons,  in  the  great  Publishing  House, 
to  whom  was  intrusted  the  mechanical  work,  for  their  faithfulness. 

Nashville,  Tenn.,  November,  1893. 


Preface  to  the  Second  Edition. 

Numerous  requests  for  a  copy  of  this  book  having  come  from  the  present 
class  in  the  Medical  Department  of  the  University  of  Nashville  and  Van- 
derbilt  University  and  from  former  graduates,  the  author  decided  to  publish 
this  special  edition.  After  a  conference  with  some  who  heard  him  deliver 
his  "Charge  to  the  Graduating  Class  of  1886-87,"  he  decided  that  he  would 
incorporate  that  address  in  this  special  edition. 

Nashville,  Term.,  December,  1S93. 


Preface  to  the  Third  Edition. 

In  presenting  the  third  edition  of  this  book  to  Ophthalmologists  the  au- 
thor -wishes  to  acknowledge  that  the  increase  in  the  size,  over  former  edi- 
tions, is  largely  due  to  the  unfavorable  criticisms  of  his  views  on  oblique 
astigmatism  and  the  oblique  muscles,  which  emanated  from  his  confreres 
Eaton,  Hotz  and  Wilson.  Mainly  because  of  these  criticisms,  Chapters 
II.,  III.,  and  IV.  have  been  inserted.  He  leaves  to  the  impartial  judgment 
of  his  readers  the  decision  as  to  the  truthfulness  of  what  he  has  taught  on 
these  subjects.  lie  wishes  to  acknowledge  his  debt  of  gratitude  to  these 
critics,  for,  in  their  own  way,  they  have  aided  him  in  presenting  more 
clearty  and  forcibly  his  thoughts  on  oblique  astigmatism  and  the  oblique 
muscles. 

In  the  preparation  of  Chapter  IV.  the  author  desires  to  acknowledge 
the  aid  given  him  by  Lowry,  his  former  pupil,  and  Perry. 

The  addition  to  Chapter  V.  makes  the  detection  of  insufficiency  of  the 
obliques  most  easy,  and  places  the  treatment  of  this  condition  on  a  sound 
scientific  basis. 

In  Chapter  VIII.  the  author  believes  that  he  has  embodied  valuable 
practical  doctrine. 

The  development  of  weak  ciliary  muscles  and  the  prevention,  or  at  least 
the  delay,  of  presbyopia  is  shown  to  be  possible  in  Chapter  IX. 

In  concluding  this  preface  the  author  wishes  to  thank  all  editors  who 
reviewed  the  first  edition.  These  reviews  were  in  the  main  kind  and  con- 
siderate. He  wishes  to  deny  the  accusation  of  the  few  who  said  that  the 
author  did  not  believe  that  Solomon  told  the  truth  when  he  said:  "There  i& 
nothing  new  under  the  sun."  Principles  are  as  old  as  the  sun,  and  to  these 
Solomon  referred.  The  author  is  not  responsible  for  the  fact  that  some  of 
the  principles  set  forth  in  Part  I.  of  this  book  were  concealed  through  so 
many  centuries,  nor  does  he  know  why  it  fell  to  his  lot  to  uncover  them. 

Nashville,  Term.,  February  24,  1S90. 


ts 

CONTENTS. 


PART  I. 

NEW  TRUTHS  IX  OPHTHALMOLOGY. 

Chapter  I.  Pagk 
The   Harmonious  Symmetric  Action  of  the  Oblique   Muscles  in  Ob- 
lique Astigmatism I 

Chapter  II. 

The  Functions  of  the  Oblique  Muscles,  Especially  as  They  are  Related 
to  Oblique  Astigmatism 24 

Chapter  III. 
The  Oblique   Muscles  as  Related  to  Oblique   Astigmatism:    Reply  to 
Dr.  Hotz's  Criticism 63 

Chapter  IV. 
Obliquity  of   Retinal   Images  in  Oblique   Astigmatism   as   Shown   by 
Photography 81 

Chapter  V. 
Insufficiencies  of  the  Oblique  Muscles  and  How  to  Correct  Them 100 

Chapter  VI. 
Relationship  Between  the  Centers  of  Accommodation  and  Convergence.   124 

Chapter  VII. 
Rhythmic    Exercise    tiie    Proper    Method  of    Developing    the  Ocular 
Muscles 142 

Chapter  VIII. 
Sthenic  and  Asthenic  Orthophoria,  and  Sthenic  and  Asthenic  Hetero- 
phoria 164 

rvii.) 


Vlll.  CONTENTS. 

Chapter  IX.  Pagb 

Can  Presbytopia  Be  Deferred    by  Rhythmic  Exercise  of  the  Ciliary 
Muscles? 172 

Chapter  X. 

The  Law  of    Projection  and  the  Artificial  and   Natural   Causes  That 
Modify  It 183; 

Chapter  XI. 
The  Monoscopter 191 


PART  II. 

CONTRIBUTIONS  TO  OLD  STUDIES. 

Chapter  I. 
Heterophoria:  and  a  Safe  Line  Drawn  between  Operative  and  Non- 
operative  Cases ;  and  the  Author's  Method  of  Operating 197 

Chapter  II. 
The  Necessity  for  Complete  Suspension  of  Accommodation  by  Mydri- 
atics in  the  Adjustment  of  Glasses 223. 


PART  III. 
OPERA  TIONS. 

Muscle  Shortening  vs.  Muscle  Advancement 243 

Indications  for,  and  Advantages  and  Technique  of,  Muscle  Shortening.  248 

A  New  Operation  for  Pterygium 252 

Artificial  Pupil  through  the  Center  of  Soft  Cataract 255 

The  Simplest  and  Best  Operation  for  the  Cure  of  Entropion  and  Tri- 
chiasis     257 

To  Narrow  the  Palpebral  Fissure 261 


PART  I, 


New  Truths  in  Ophthalmology. 


CHAPTER   I. 

THE  HARMONIOUS  SYMMETRIC  ACTION  OF  THE 
OBLIQUE  MUSCLES  IN  ALL  CASES  OF  OBLIQUE 
ASTIGMATISM.*  

More  than  four  years  ago  I  became  convinced  from  ob- 
servation that  a  revolution  of  the  eyes,  on  their  anteropos- 
terior axes  of  rotation,  for  the  improvement  of  vision,  occurs 
in  all  cases  of  oblique  astigmatism.  This  conviction  led  me 
to  develop  a  theory  of  revolution,  which  I  made  public  for 
the  first  time  in  a  paper  entitled  "  The  Function  of  the  Ob- 
lique Muscles  in  Certain  Cases  of  Astigmatism,"  read  be- 
fore the  Section  of  Ophthalmology  of  the  American  Medical 
Association,  at  its  Chicago  meeting  in  1887.  A  year  later  I 
wrote  a  second  paper  in  reply  to  a  paper  on  "  Binocular  As- 
tigmatism," read  by  Dr.  H.  Culbertson  before  the  Section 

*Read  before  the  Nashville  Academy  of  Medicine,  January  15,  1891. 

(1) 


2  ACTION  OF  THE  OBLIQUE  MUSCLES 

of  Ophthalmology,  at  the  Cincinnati  meeting  of  the  Ameri- 
can Medical  Association,  in  which  I  advocated  the  same 
theory  of  rotation  as  set  forth  in  my  first  paper,  and  by  it 
accounted  for  all  the  phenomena  referred  to  in  Dr.  C.'s  pa- 
per, viz.,  loss  of  parallelism  of  the  sides  of  a  rectangle, 
slanting  of  a  level  surface,  etc. 

In  developing  my  theory  of  rotation,  I  believed  the  teach- 
ing to  be  true  that,  under  all  circumstances,  the  naturally 
vertical  meridians  of  the  corneas  must  be  kept  parallel,  or 
double  vision  would  result.  I  therefore  reasoned  that,  in 
rotating,  both  eyes  must  roll  in  the  same  direction.  This 
could  be  effected  only  by  the  superior  oblique  of  one  eye 
acting  with  the  inferior  oblique  of  the  other;  and  this  action 
I  termed  "  harmonious  non-symmetrical." 

At  that  time  the  condition  necessitating  this  revolving  of 
the  eyes  was  not  clear  to  me.  I  contented  myself  by  believ- 
ing that  the  retinal  image  was  thereby  sharpened.  That  ob- 
lique astigmatism  involves  the  necessity  of  abnormal  action 
on  the  part  of  the  oblique  muscles,  I  will  be  able  to  prove  in 
this  paper,  thus  taking  the  rotation  of  the  eyes  on  their  an- 
tero-posterior  "  axes  of  rotation  "  out  of  the  domain  of  theo- 
ry and  placing  it  in  that  of  fact. 

What  is  astigmatism  ?  I  cannot  hope  to  answer  this  ques- 
tion more  clearly  than  it  is  answered  in  many  of  the  books 
on  the  eye.  But  many  of  you,  not  being  Ophthalmic  Sur- 
geons, possibly  have  never  read  the  chapter  on  astigmatism. 


IN   OBLIQUE   ASTIGMATISM.  3 

An  astigmatic  eye  is  one  whose  cornea  has  not  the  same 
radius  of  curvature  for  all  its  parts.  That  part  of  the  cor- 
nea having  the  shortest  radius  is  the  most  rapidly  curved; 
while  the  part  with  the  longest  radius  is  the  least  rapidly 
curved.  These  two  parts  are  always  at  right  angles  the  one 
to  the  other.*  As  a  rule  the  meridian  of  greatest  curvature  is 
in  the  vertical  or  nearly  so ;  while  the  meridian  of  least  cur- 
vature is  nearly  or  quite  horizontal.  As  we  go  from  the 
meridian  of  greatest  toward  the  meridian  of  least  curvature 
we  find  every  meridian  less  rapidly  curved,  hence  each 
having  a  longer  radius  than  the  one  preceding  it. 

The  law  of  refraction  by  curved  surfaces  I  will  illustrate 
by  supposing  that  we  have  before  us  two  spheres  of  crown 
glass,  one  having  a  radius  of  two  inches,  and  the  other  a  ra- 
dius of  one  inch.  Parallel  rays  of  light,  on  entering  either 
of  these  spheres,  will  undergo  such  a  bend  at  the  points 
of  entrance  as  will  bring  them  to  a  focus  at  the  opposite  ex- 
tremity of  the  diameter  of  the  sphere.  The  larger  sphere, 
having  a  diameter  of  four  inches,  has,  therefore,  a  focal 
power  of  four  inches;  the  smaller  sphere,  having  a  diameter 
of  two  inches,  has  a  focal  power  of  two  inches.  The  den- 
sity of  the  one  sphere  being  the  same  as  the  density  of  the 
other,  the  difference  in  focal  power  is  due  solely  to  the 
want  of  similarity  in  curvature.     The  more  rapidly  curved 

*The  Ophthalmometer  sometimes  shows  a  slight  variation  from  this 
rule. 


4  ACTION   OF   THE   OBLIQUE   MUSCLES 

surface  has  the  shorter  focus ;  the  least  rapidly  curved 
surface,  the  longer  focus. 

As  already  defined,  astigmatism  is  due  to  a  want  of  simi- 
larity of  curvature  of  the  different  parts  of  the  cornea. 

Figure  A  is  intended  to  represent  an  astigmatic  eye.  The 
continuous  and  dotted  curved  lines  to  the  left  represent  the 
meridians    of   greatest  and  least  curvature   of  the   cornea, 


Figure  A. 

known  in  ophthalmology  as  the  two  principal  meridians. 
These  must  be  considered  as  at  right  angles  to  each  other. 
The  continuous  line,  which  is  the  more  rapidly  curved,  we 
will  consider  as  the  vertical  meridian  of  the  cornea;  and  as 
such  it  is  destined  to  refract  the  rays  of  light  entering  the 
eye  in  the  vertical  plane.  The  two  continuous  parallel  lines 
represent  this  plane  of  rays ;  and  these,  as  shown  in  the  figure, 
are  so  bent  by  this  curved  surface  as  to  be  brought  to  a  fo- 
cus on  the  retina,  represented  by  the  continuous  curved  line 


IN   OBLIQUE   ASTIGMATISM.  5 

to  the  right.  The  broken  curved  line  to  the  left,  represent- 
ing the  horizontal  meridian  of  the  cornea,  is  less  rapidly 
curved,  and  therefore  so  refracts  the  rays  of  light  entering 
the  eye  in  a  horizontal  plane  (these  are  represented  by  the 
two  broken  parallel  lines),  as  to  give  them  a  longer  focal 
distance.  You  see  them  brought  to  a  focus  on  the  dotted 
curved  line  to  the  right,  some  distance  behind  the  contin- 
uous line  representing  the  retina.  This  difference  in  focal- 
izing power  affects  alike  both  divergent  and  parallel  rays  of 
light. 

To  have  a  perfect  image  of  any  external  object  formed  on 
the  retina,  all  the  rays  emanating  from  any  one  point  of  the 
object  must  be  brought  to  one  point  oh  the  retina.  For 
this  to  be,  the  cornea  must  be  a  section  of  a  perfect  sphere, 
all  the  meridians  having  the  same  radius  of  curvature.  It 
is  clear,  then,  that  an  unaided  astigmatic  eye  cannot  have  a 
well-defined  image  of  any  object  formed  on  its  retina. 

I  need  only  mention  that,  in  the  two  forms  of  hyperme- 
tropic astigmatism,  the  corneal  meridian  of  greatest  curva- 
ture is  the  best  meridian,  the  focus  for  its  rays  being  on  the 
retina  (as  in  simple  hypermetropic  astigmatism),  or  a  little 
way  behind  it  (as  in  compound  hypermetropic  astigmatism)  ; 
while  the  focus  for  the  meridian  of  least  curvature  is  always 
more  distant. 

In  myopic  astigmatism,  whether  simple  or  compound,  the 
meridian  of  greatest  curvature  is  always  the  zcors/  meridian. 


6  ACTION   OF   THE   OBLIQUE   MUSCLES 

In  the  fifth  and  last  form,  mixed  astigmatism,  the  most  rap- 
idly curved  meridian  is  the  myopic;  the  least  rapidly 
curved,  the  hypermetropic. 

If  you  were  all  Ophthalmic  Surgeons,  it  would  be  superflu- 
ous for  me  to  add  that  regular  astigmatism,  which  includes 
the  five  kinds  just  mentioned,  is  congenital  in  its  origin ;  and 
its  duration  is  commensurate  with  the  lifetime  of  the  individ- 
ual. While  there  are  opinions  to  the  contrary,  it  is  the  con- 
viction of  the  author  of  this  paper  that,  so  long  as  the  astig- 
matic cornea  remains  free  from  pathological  changes,  the 
kind  and  quantity  of  the  astigmatism  remain  invariable. 
That  is  to  say,  the  radii  of  curvature  of  the  two  principal 
meridians  bear  at  all  times  the  same  relationship  to  each 
other. 

What  effect  has  astigmatism  on  the  retinal  image?  Sup- 
pose the  object  looked  at  to  be  a  line  occupying  a  position 
at  right  angles  to  the  meridian  of  best  curvature.  Its  image 
will  be  more  or  less  sharp,  depending  on  the  quantity  of  as- 
tigmatism, except  at  its  two  extremities,  which  will  be 
blurred.  If  the  line  corresponds  to  the  best  meridian,  the 
whole  image  is  so  marred  that  the  line  is  not  well  seen.  If 
the  two  principal  meridians  are  respectively  vertical  and  hor- 
izontal, the  retinal  image  of  a  horizontal  or  vertical  object  is 
unaffected  except  in  sharpness  of  outline  as  indicated  above. 

In  all  cases  of  oblique  astigmatism  there  is  something 
more  than   a  simple  blurring  of  the  image.     In   eyes  free 


IN   OBLIQUE   ASTIGMATISM.  7 

from  astigmatism,  and  even  in  astigmatic  eyes  when  the  prin- 
cipal meridians  are  vertical  and  horizontal,  the  horizontal 
object  and  the  retinal  image  are  always  in  the  same  plane. 
In  oblique  astigmatism,  be  the  obliquity  much  or  little,  it  is  a 
physical  impossibility  for  the  horizontal  object  and  its  reti- 
nal image  to  occupy  the  same  plane.  The  same  is  true  of 
all  objects  not  in  a  plane  with  one  or  the  other  of  the  two 


RIGHT 


LEFT 


principal  meridians.     There  is,  therefore,  not  only  blurring, 
but  also  obliquity  of  the  image. 

Figure  I  represents  a  pair  of  eyes  in  which  the  two  prin- 
cipal meridians  are  vertical  and  horizontal  (they  can  also 
represent  eyes  that  are  non-astigmatic).  If  before  these 
eyes  an  arrow,  or  the  picture  of  an  arrow,  be  held  horizon- 
tally, the  arrowhead  toward  the  patient's  left,  it  will 
throw  a  reversed  image  on  each  retina,  and  the  two  images 
will  be  in  the  same  plane  with  the   object.     These  two  im- 


8 


ACTION   OF   THE   OBLIQUE   MUSCLES 


ages  fall  on  parts  of  the  two  retinas  that  act  together,  hence 
but  one  object  is  seen. 

Figure  2  represents  a  pair  of  eyes  in  which  there  is  hyper- 


RIGHT 


RIGHT 


LEFT 


LEFT 


metropic  astigmatism,  either  simple  or  compound.  The  left 
eye  has  its  best  meridian  vertical.  In  this  eye  the  arrow, 
held  as  before,  throws  its  image  on  the  horizontal  meridian 
of  the  retina,  hence  in  the  same  plane  with  it.     In  the  right 


IN   OBLIQUE   ASTIGMATISM. 


eye  the  best  meridian  is  at  1350,  as  shown  by  the  dotted  line. 
In  obedience  to  the  well-known  law  of  refraction  by  curved 
surfaces,  the  image  of  the  same  arrow  must  be  oblique  in 


Fig- 4 


RIGHT 


LEFT 


LEFT 


this  eye,  and  hence  not  in  the  same  plane  with  the  object. 
The  obliquity  of  the  image  will  be  greater  or  less,  depending 
on  the  quantity  of  the  astigmatism.  I  represent  it  as  falling 
on  meridian  1700  of   the    retina.      The  horizontal   image   in 


IO 


ACTION   OF   THE   OBLIQUE    MUSCLES 


the  left  eye  and  the  oblique  image  in  the  right  eye  do  not 
fall  on  parts  of  the  two  retinae  that  harmonize.  The  direc- 
tion   of  either  image   in   relation    to    the    other    cannot    be 


RIGHT 


RIGHT 


Fig.6 


tig-'.       * 


LEFT 


LEFT 


changed  except  by  artificial  means — a  proper  cylindrical 
lens.  This  being  true,  the  pair  of  unaided  astigmatic  eyes, 
represented  by  Figure  2,  must  see  the  arrow  double,  as 
shown  in  Figure  8,  unless  something  is  done  by  the   eyes 


IN   OBLIQUE   ASTIGMATISM.  II 

themselves    for    the    purpose    of   harmonizing  the   images. 
What  is  done  will  be  shown  later. 

Figure  4  represents  a  pair  of  hypermetropic  astigmatic 
eyes,  the  left  one  having  its  best  meridian  vertical,  and  the 
right  one  having  its  best  meridian  at  450.  In  these  eyes 
there  is  a  left  horizontal  image  (image  and  arrow  in  same 
plane)  and  a  right  oblique  image,  this  time  on  retinal  me- 
ridian io°.  Nothing  but  artificial  means  will  change  the 
relative  direction  of  these  images ;   and  there  must  be  double 


Figure  8. 


vision,  unless  the  oblique  image  can  be  made  to  fall  on  a  por- 
tion of  the  retina  that  will  harmonize  with  that  portion  of 
the  other  retina  on  which  the  horizontal  image  may  fall. 

Figure  6  represents  a  pair  of  hypermetropic  astigmatic 
eyes,  with  half  the  quantity  of  astigmatism  found  in  the  eyes 
represented  by  Figures  2  and  4;  but  in  both  eyes  the  best 
meridian  is  oblique,  in  the  left  at  450,  and  in  the  right  at 
I35°-  An  arrow  held  in  the  horizontal  position  before  these 
eyes  will  throw  an  oblique  image  on  each  retina;  the  one  in 
the  left  eye  on  meridian  50,  and  the  one  in  the  right  on  me- 
ridian 1750.  Without  some  change  double  vision,  as  shown 
in  Figure  8,  will  be  inevitable. 


12  ACTION   OF   THE   OBLIQUE   MUSCLES 

In  the  same  way  I  could  demonstrate  the  obliquity  of  ret- 
inal images  in  oblique  myopic  astigmatism.  The  rule  in  ob- 
lique astigmatism,  without  a  single  exception,  is  this:  The 
retinal  image  is  displaced  toward  the  meridian  of  greatest 
curvature;  therefore,  in  oblique  hypermetropic  astigmatism, 
the  image  is  displaced  toward  the  meridian  of  best  curvature; 
in  myopic  astigmatism,  from  the  meridian  of  best  curva- 
ture; and  in  oblique  mixed  astigmatism,  toward  the  myopic 
meridian. 

The  obliquity  of  the  image  in  oblique  astigmatism  is  de- 
monstrable. One  wrho  is  emmetropic,  or  at  least  is  nonastig- 
matic,  by  placing  a  — 3  D.  cyl.  before  each  eye  in  trial 
frames,  creates  3  dioptres  of  hypermetropic  astigmatism. 
The  axis  of  the  left  cylinder  being  at  900  and  that  of  the 
right  at  1350,  he  has  made  of  his  own  eyes  the  kind  repre- 
sented by  Figure  2.  He  may  now  for  a  moment  place  the 
opaque  disk  in  front  of  his  right  eye,  at  the  same  time  plac- 
ing the  double  prism  (each  6°)  before  the  left  eye.  A  hor- 
izontal arrow,  head  to  left,  having  been  drawn  on  a  card 
board,  he  looks  through  his  double  prism  and  sees  two  hor- 
izontal, hence  parallel,  arrows.  On  removing  the  opaque 
disk  from  the  right  side  of  the  trial  frame,  a  third  arrow  ap- 
pears between  the  other  two.  but  not  parallel  with  them — it 
is  oblique  down  and  to  the  patient's  left.  On  removing  the 
double  prism  two  arrows  are  at  once  readily  seen,  the  one 
crossing  the  other  as  in  Figure  8.     In  a  moment  the  two  ar- 


IN   OBLIQUE   ASTIGMATISM.  13 

rows  begin  to  shut  and  open  like  the  blades  of  a  pair  of 
scissors;   and  finally  they  are  merged  indefinitely  into  one. 

What  efforts  are  made  by  the  eyes  for  the  correction  of 
astigmatism V  In  some  forms  of  astigmatism,  the  ciliary 
muscle  labors  to  improve  the  state  of  vision,  to  sharpen  the 
retinal  image.  When  the  rays  of  light  come  to  the  eye  par- 
allel, no  form  of  ciliary  strain  can  improve  the  vision  in  my- 
opic astigmatism,  simple  or  compound.  For  divergent  rays 
in  low  degrees  of  myopic  astigmatism,  regular  ciliary  con- 
traction may  so  act  on  the  lens  as  to  cause  the  focal  interval 
to  fall  on  the  retina,  whereby  a  sharper  retinal  image  is 
formed. 

In  hypermetropic  astigmatism,  the  rays  of  light  being 
either  parallel  or  divergent,  regular  ciliary  contraction  can 
so  act  on  the  lens  as  to  make  the  focal  interval  fall  on  the 
retina,  and  thus  sharpen  vision. 

In  myopic  astigmatism  the  best  meridian  being  either  in 
the  horizontal  or  vertical,  there  can  be  no  strain  in  distant 
seeing,  for  no  kind  of  strain  would  improve  the  vision;  but 
there  may  be  ciliary  strain  in  near  vision.  In  hypermetropic 
astigmatism,  non-oblique,  there  is  only  ciliary  strain  both  for 
distant  and  near  seeing. 

Sectional  contraction  of  the  ciliary  muscle  for  the  partial 
or  complete  correction  of  astigmatism  has  its  advocates. 
Martin  developed  the  theory.  The  ciliary  muscle  is  sup- 
posed to  act  in  two  opposite  sections ;  while  the  balance  of 


14  ACTION   OF   THE   OBLIQUE    MUSCLES 

this  circular  muscle  remains  quiet,  or  is  in  a  slighter  state  of 
action.  The  parts  in  greatest  action  are  supposed  to  coin- 
cide with  the  corneal  meridian  of  least  curvature.  It  is  ar- 
gued that  in  this  way  lenticular  astigmatism  is  produced,  of 
the  same  kind  as,  but  at  right  angles  to,  the  corneal  astigma- 
tism. If  this  be  true,  then  in  non-oblique  myopic  astigma- 
tism, distant  seeing  is  not  attended  by  sectional  ciliary  con- 
traction, since  it  would  make  vision  worse  and  not  better — 
distant  vision  in  simple  myopic  astigmatism  of  i  D.  is  better 
than  when  there  is  I  D.  of  simple  myopia.  The  object  of 
all  eye-strain  is  to  improve  vision;  and  when  this  cannot  be 
effected,  the  strain  is  not  instituted.  In  myopic  astigmatism 
near  vision  would  be  greatly  improved  by  sectional  ciliary 
strain. 

In  hypermetropic  astigmatism  sectional  ciliary  contrac- 
tion could  sharpen  both  distant  and  near  vision.  Grant- 
ing that  there  may  be,  now  and  then,  a  case  of  "  masked  " 
hypermetropic  astigmatism,  which  would  point  to  the 
correctness  of  Martin's  theory  of  sectional  ciliary  con- 
traction, the  great  mass  of  evidence  gathered  from  daily  ob- 
servations, by  whomsoever  made,  goes  to  prove  that  there 
is  no  truth  in  his  theory. 

In  all  cases  of  oblique  astigmatism,  unless  the  obliquity  is 
in  the  same  direction  in  the  two  eyes,  and  the  astigmatism 
the  same  in  kind  and  quantity,  something  must  be  done  in 
order  to  prevent  double  vision,  as  represented  in  Figure  8. 


IN   OBLIQUE   ASTIGMATISM.  I  5 

There  are  but  two  ways  of  accounting  for  the  absence  of 
this  peculiar  kind  of  double  vision  in  such  forms  of  astig- 
matism as  that  represented  in  Figures  2  and  4.  Sectional 
ciliary  contraction  would  account  for  it.  If  it  were  possible 
for  the  ciliary  muscle  thus  to  act,  one  can  readily  under- 
stand how  the  curvature  of  the  lens  could  be  so  changed 
as  to  result  in  lenticular  astigmatism  equal,  but  at  right  an- 
gles, to  the  corneal  astigmatism.  If  such  ciliary  action  were 
to  take  place  in  the  right  eye  of  either  Figure  2  or  4,  the  ret- 
inal image  would  not  only  be  made  as  sharp  as  if  in  an  em- 
metropic eye,  but  it  would  also  be  made  to  lose  its  obliquity, 
and  thus  double  vision  would  be  prevented.  As  beautifully 
as  this  sectional  ciliary  action  would  account  for  the  absence 
of  double  vision  in  cases  of  oblique  astigmatism,  it  is  cer- 
tainly a  false  theory,  since,  when  all  ciliary  power  has  been 
suspended  by  atropine  or  age,  the  eyes  are  still  able  to  do 
something  by  means  of  which  the  double  vision  represented 
by  Figure  8  is  prevented. 

If  sectional  ciliary  contraction  does  not  occur,  then  the 
two  eyes  represented  by  Figure  2  or  4  have  no  inherent 
power  by  means  of  which  the  relative  direction  of  the  two 
retinal  images  can  be  changed;  hence  there  must  be  double 
vision,  unless  the  oblique  image  in  the  right  eye  and  the  hor- 
izontal image  in  the  left  can  be  made  to  occupy  correspond- 
ing parts  of  the  two  retinas.  This  can  be  effected  alone  by 
the  harmonious  symmetrical  action  of  the  oblique  muscles. 


l6  ACTION   OF   THE   OBLIQUE   MUSCLES 

Figure  3  shows  how  the  eyes  represented  by  Figure  2  act 
in  order  to  have  the  images  fall  on  corresponding  parts  of 
the  retinas.  The  superior  oblique  muscle  of  the  right  eye 
has  so  revolved  it  as  to  bring  meridian  1750  of  the  retina  in 
position  to  receive  the  impress  of  the  oblique  image;  while 
at  the  same  moment  the  superior  oblique  muscle  of  the  left 
eye  has  so  revolved  it  as  to  bring  meridian  175°  to  the  hori- 
zontal, hence  in  position  to  receive  the  horizontal  image. 
The  oblique  and  horizontal  images  being  now  on  harmoniz- 
ing portions  of  the  retinae,  there  is  no  double  vision. 

The  double  vision  that  would  exist  in  astigmatic  eyes  rep- 
resented in  Figure  4  is  prevented  by  the  harmonious  action 
of  the  inferior  oblique  muscles,  as  shown  by  Figure  5,  the  in- 
ferior oblique  of  the  right  eye  bringing  meridian  50  under 
the  oblique  image,  while  the  inferior  oblique  of  the  left  eye 
causes  meridian  50  to  come  under  the  horizontal  image. 
Thus  the  two  images  are  made  to  fall  on  corresponding 
parts  of  the  two  retinae. 

In  the  oblique  astigmatism  of  the  two  eyes  represented  by 
Figure  6,  the  two  oblique  images  are  made  to  fall  on  corre- 
sponding parts  of  the  retina?  by  the  harmonious  action  of  the 
two  superior  oblique  muscles,  as  shown  in  Figure  7. 

The  obliquity  of  the  image  and  the  consequent  strain  on 
the  oblique  muscles  fully  account  for  the  greater  trouble  at- 
tending oblique  astigmatism  than  is  found  connected  with 
astigmatism  in  the  vertical   or  horizontal.     As  has  already 


IN  OBLIQUE   ASTIGMATISM.  1 7 

been  shown  in  this  paper,  non-oblique  myopic  astigmatism  is 
unattended  by  any  sort  of  strain  in  distant  vision. 

In  oblique  myopic  astigmatism,  there  is  strain  on  either 
the  two  superior  or  two  inferior  oblique  muscles  in  both  dis- 
tant and  near  seeing.  In  all  other  forms  of  oblique  astigma- 
tism, there  is  likewise  strain  on  the  oblique  muscles. 

In  all  kinds  of  non-oblique  astigmatism,  also  in  simple  hy- 
permetropia,  the  time  comes  when  all  nervous  phenomena 
caused  by  their  existence  pass  away.  Their  disappearance, 
being  gradual  but  finally  complete,  coincides  with  the  fail- 
ure and  final  loss  of  ciliary  power  brought  about  by  ad- 
vancing age.  The  symptoms  caused  by  oblique  astigma- 
tism may  be  modified  by  old  age  putting  at  rest  the  ciliary 
muscles,  but  they  cannot  be  made  to  vanish;  for  the  oblique 
muscles  are  forced  to  continue  to  act  in  age  as  in  youth,  so 
as  to  harmonize  the  images  on  the  two  retince. 

It  is  easy  to  account  for  the  little  suffering  endured  by 
one  person  with  a  certain  quantity  of  astigmatism  oblique  in 
a  certain  direction,  while  another  person  with  the  same  con- 
dition of  refraction  is  a  greater  sufferer.  Let  us  suppose 
two  persons  having  eyes  represented  by  Figure  2.  The  ne- 
cessity for  overaction  or  abnormal  action  is  on  the  superior 
oblique  muscles.  In  the  case  of  the  one  who  suffers  but 
little  the  superior  obliques  are  powerful  and  can  bear  the 
necessary  strain  without  generating  a  train  of  nervous  phe- 
nomena; in  the  other  patient  the  superior  oblique  muscles 
2 


lb  ACTION  OF  THE  OBLIQUE  MUSCLES 

are  feeble,  and  the  necessary  overwork  is  attended  by  peri- 
odical waves  of  suffering. 

The  propriety— I  may  say  the  necessity— of  correcting 
non-oblique  astigmatism  by  means  of  cylindrical  lenses  is 
now  universally  acknowledged.  Such  a  lens  sharpens  the 
retinal  image,  thus  making  the  object  clear  and  distinct,  and 
at  the  same  time  removes  the  necessity  for  abnormal  ciliary 
strain.  In  youth,  headaches  and  other  symptoms,  whose  ex- 
istence depends  on  this  strain,  vanish  as  if  by  magic  when 
the  correct  cylindrical  lenses  are  worn.  Otherwise  old  age 
alone  would  relieve  the  sufferer  without  being  able  to 
sharpen  the  image. 

In  oblique  astigmatism  the  correcting  lens  both  sharpens 
the  retinal  image  and  causes  it  to  lose  its  obliquity,  thus,  at 
one  stroke,  destroying  the  necessity  for  abnormal  ciliary 
strain  and  for  overaction  on  the  part  of  the  oblique  muscles. 
The  one  set  of  symptoms  whose  existence  is  lost  in  advanc- 
ing age,  and  the  other  set  whose  duration  is  commensurate 
with  the  length  of  life,  are  made  to  disappear  by  the  power 
of  the  c}dindrical  lens. 

In  the  several  cuts  showing  the  effect  of  oblique  astigma- 
tism on  the  retinal  image  of  a  horizontal  arrow,  the  best  me- 
ridian is  450  either  out  or  in  from  the  vertical.  This  posi- 
tion for  the  meridian  of  greatest  curvature  was  chosen  be- 
cause, for  any  given  quantity  of  astigmatism,  the  obliquity 
of  the  retinal  image  is  greatest  here.     If  there  are   several 


IN  OBLIQUE   ASTIGMATISM.  T9 

cases  of  hypermetropic  astigmatism  of  3  D.  each,  one  of 
these,  having  its  best  meridian  at  ioo°  (or  8o°),  will  have  a 
retinal  image  only  slightly  oblique ;  another,  with  its  best  me- 
ridian at  no°  (or  700),  will  have  more  obliquity  of  its  retinal 
image;  and  so  on,  until  the  case  is  reached  in  which  the  best 
meridian  is  at  1350  (or  450).  Here  the  maximum  of  obliquity 
of  the  image  is  reached.  In  the  remaining  cases,  the  best  me- 
ridians are  between  1350  (or  450)  and  the  horizontal;  and 
the  nearer  these  are  to  the  horizontal,  the  less  oblique  are 
the  images.  What  is  true  of  hypermetropic  astigmatism  is 
also  true  of  the  myopic  and  mixed  forms  of  astigmatism. 
The  obliquity  of  the  image  varies  not  only  with  the  differ- 
ence in  position  of  the  meridian  of  greatest  curvature,  but 
also  with  varying  quantities  of  astigmatism.  The  image 
will  not  be  so  oblique  if  there  is  1  D.  of  astigmatism  with  its 
best  meridian  at  135°  (or  450)  as  when  there  are  2  D.  in  the 
same  direction.  The  amount  of  obliquity  of  the  retinal  im- 
age of  any  horizontal  object  varies,  in  any  given  quantity  of 
astigmatism,  with  the  more  or  less  remote  position  of  the 
meridian  of  greatest  curvature  from  the  vertical  or  horizon- 
tal up  to  450;  also  with  the  quantity  of  astigmatism,  the  best 
meridian  being  at  some  fixed  angle  between  the  vertical  and 
horizontal.  In  small  degrees  of  astigmatism,  the  obliquitv 
of  the  image  can  be  but  a  few  minutes,  while  in  the  higher 
degrees  the  obliquity  is  50  or  more.  In  some  of  the  figures 
used  illustrating  this  paper,  the  obliquity  of  the  image  is  rep- 


20  ACTION  OF  THE  OBLIQUE  MUSCLES 

resented  as  being  as  much  as  io°,  only  for  convenience  of 
illustration. 

All  errors  of  refraction  should  be  corrected  by  the  ex- 
amination of  only  one  eye  at  a  time,  an  opaque  disk  be- 
ing placed  in  front  of  the  other  eye;  and  the  eyes  should 
be  under  the  influence  of  a  mydriatic,  unless  ciliary  strain 
has  been  suspended  by  age.  Especially  should  this  be  the 
plan  of  procedure  in  all  cases  of  oblique  astigmatism.  It  is 
in  cases  of  oblique  astigmatism  that  oculists  find  trouble 
in  locating  the  axis  of  the  cylinder,  at  one  moment  the  pa- 
tient indicating  that  it  should  be  at  a  certain  angle,  and  at 
the  next  moment  50  or  more  removed  from  this  point.* 
Enough  time  should  be  spent,  and  sufficient  care  exercised,  to 
enable  the  operator  to  determine  the  natural  location  of  the 
best  meridian;  and  at  this  angle  the  axis  of  the  cylinder 
should  always  be  placed.  If  the  best  meridian  in  hyper- 
metropic astigmatism  is  in  the  temporal  quadrant,  and  there 
is  doubt  as  to  whether  the  axis  of  the  cylinder  should  be 
placed  at  a  certain  angle  or  50  nearer  the  horizontal,  the  lat- 
ter should  be  chosen;  for  in  such  a  case  the  superior  ob- 
lique, from  long  habit,  wants  to  continue  to  revolve  the  eye 
in  an  abnormal  but,  without  the  proper  cylinder,  necessary 
position.     The  point  to  be  chosen  for  the   location  of  the 

*We  have  also  been  able  to  show  that  insufficiency  of  the  obliques  adds 
to  the  difficulty  of  properly  placing  the  axis  of  the  cylinder.  See  chapter  on 
Insufficiency  of  the  Obliques. 


IN  OBLIQUE   ASTIGMATISM.  21 

axis  of  the  cylinder  in  myopic  astigmatism  is  always  the  re- 
verse of  that  for  hypermetropic  astigmatism — I  mean  where 
there  is  doubt  between  any  two  points. 

Each  of  the  two  eyes  in  which  there  is  oblique  astigma- 
tism having  thus  been  carefully  corrected,  the  proper 
glasses  are  ordered.  When  the  patient  begins  to  wear 
them,  his  binocular  single  vision  is  nearly  always  disturbed 
by  an  apparently  changed  condition  of  objects,  a  rectangle 
no  longer  appearing  to  be  such,  and  a  level  surface  seeming 
to  incline.  Sometimes  the  changes  are  so  marked  as  to 
make  the  patient  very  uncomfortable.  This  metamorphop- 
sia  (so  termed  by  Dr.  Lippincott,  of  Pittsburg)  may  con- 
tinue a  few  hours,  a  day,  a  week,  or  a  month,  but  in  the 
end  is  certain  to  disappear  It  is  due  to  a  continuation  of 
the  old  habit  of  rotation,  when  both  eyes  are  used,  and  a 
consequent  loss  of  coincidence  of  the  best  meridians  and  the 
axes  of  the  cylinders.  Whenever  this  now  unnecessary 
habit  of  rotation  is  broken,  be  it  soon  or  late,  sudden  or 
gradual,  the  metamorphopsia  ceases.  The  different  forms 
of  metamorphopsia  can  be  demonstrated  artificially. 

Four  years  ago  I  said  that  in  cases  of  oblique  astigmatism 
the  eyes  were  made  to  rotate  by  means  of  the  oblique  mus- 
cles. I  repeat  the  assertion  to-day  with  emphasis,  but  with 
this  modification:  I  then  thought  the  rotation  was  effected 
by  the  harmonious  non-symmetrical  motion  of  the  obliques; 
but  in  this  paper  I  have   demonstrated   that  the  rotation  is 


22  ACTION   OF   THE   OBLIQUE   MUSCLES 

brought  about  by  the  harmonious  symmetrical  action  of  the 
obliques,  and  have  also  shown  why  the  rotation  is  necessary. 
The  only  papers  ever  published,  touching  this  question,  so 
far  as  I  know,  except  my  own  already  referred  to,  are:  one 
on  "  Binocular  Astigmatism,"  by  Dr.  H.  Culbertson,  in  the 
Journal  of  the  Association,  November  3,  1888;  and  one  on 
"  Metamorphopsia,"  by  Dr.  J.  A.  Lippincott,  in  the  Ar- 
chives of  Ophthalmology,  March,  1889.  The  latter  is  a  valu- 
able paper,  and  shows  the  Doctor  to  be  a  close  observer  as 
well  as  a  ready  writer.  In  his  paper  he  incidentally  refers 
to  the  obliquity  of  the  retinal  image  in  oblique  astigmatism, 
but  does  not  advocate  the  doctrine  of  rotation. 


Founded  on  the  teachings  of  this  paper,  Dr.  N.  C.  Steele, 
of  Chattanooga,  formulated  the  following  working  rule: 

"  In  those  cases  in  which  the  axes  of  the  proper  convex  cyl- 
inders/or the  two  eyes  diverge,  place  the  cylinders  at  those 
points  which  will  give  the  axes  the  greatest  divergence  per- 
mitted by  the  tests;  and  in  those  cases  in  which  the  axes  con- 
verge, place  them  at  the  points  which  will  give  them  the 
greatest  convergence  permitted  by  the  tests." 

In  oblique  myopic  astigmatism  the  placing  of  the  axes  of 
the  concave  cylinders  is  governed  by  the  above  rule,  modi- 
fied by  substituting  least  for  greatest  and  vice  versa  wherever 
it  occurs.     This  rule  is  applicable  only  in  those  cases  where 


IN  OBLIQUE   ASTIGMATISM.  23 

there  is  doubt  as  to  the  location  of  the  axes.  When  one  eye 
of  a  pair  of  oblique  astigmatic  eyes  is  covered,  the  strained  ob- 
lique muscles  do  not  always  relax;  and  when  this  is  the  case, 
the  cylinder  given  does  not  relieve  the  strain,  however  sharp 
it  may  make  the  vision.  In  some  cases,  the  obliques  do  relax, 
one  eye  being  covered,  and  the  cylinders  are  readily  so  placed 
as  to  relieve  all  strain.  In  these  two  conditions  the  answers 
of  the  patients  throw  no  doubt  on  the  question  of  location  of 
the  axes  of  the  cylinders.  There  are  other  cases,  and  they 
are  numerous,  in  which  there  is  alternating  contraction  and 
relaxation  of  the  obliques,  the  one  eye  being  covered  while 
the  other  is  under  observation.  At  one  moment  the  patient 
declares  that  he  sees  best  with  the  cylindrical  axis  at  one 
point,  and  at  the  next  moment  he  selects  a  point  50  removed. 
This  is  kept  up  until  no  conclusion  can  be  reached,  unless 
the  operator  has  knowledge  of  the  nature  of  oblique  astig- 
matism. It  is  in  such  cases  as  these  that  Dr.  Steele's  rule 
may  be  safely  followed;  and  that,  too,  without  having  to 
stop  to  determine  whether  the  superior  or  inferior  obliques 
are  the  strained  pair. 


CHAPTER  II. 

THE  FUNCTIONS  OF  THE  OBLIQUE  MUSCLES,  ES- 
PECIALLY AS  THEY  ARE  RELATED  TO  OB- 
LIQUE ASTIGMATISM.* 

The  common  purpose  of  all  the  extrinsic  ocular  muscles 
is  the  production  of  binocular  single  vision,  in  obedience  to 
the  law  of  corresponding  retinal  points.  The  recti  muscles 
are  designed  to  control  the  visual  axes,  while  the  obliques 
are  concerned  with  the  corneo-retinal  meridians.  In  model 
eyes  a  plane  may  be  constructed  so  as  to  cut  the  macula  and 
the  nodal  point  of  each  eye  and  that  point  of  the  object  to 
be  fixed.  The  superior  and  inferior  recti  must  keep  the  two 
visual  axes  in  this  plane,  while  the  external  and  internal 
recti  must  direct  them  so  that  they  may  intersect  at  the  point 
to  be  fixed.  Since,  in  all  eyes  free  from  oblique  astigmatism, 
all  other  visual  lines  bear  a  definite  relationship  to  the  visual 
axis,  they  may  be  ignored  in  any  study  of  the  ocular  mus- 
cles. If  the  recti  muscles,  in  accomplishing  the  purpose  of 
their  existence,  effected  no  other  change  of  the  eyes,  there 
would  be  no  need  for  oblique  muscles  in  eyes  not  having 

*Republished  from  the  Proceedings  of  the  Eighth  International  Con- 
gress of  Ophthalmology. 

(24) 


THE   FUNCTIONS   OF   THE   OBLIQUE   MUSCLES.  25 

■oblique  astigmatism.  The  three  axes  of  rotation  are  at  right 
angles  to  one  another,  their  point  of  intersection  being  the 
nodal  point — the  center  of  retinal  curvature.  The  lateral  recti 
muscles,  if  properly  attached  to  the  globe,  will  rotate  it  only 
on  the  perpendicular  axis ;  the  superior  and  inferior  recti 
could  not,  if  unopposed,  effect  the  rotation  of  the  eye  on  its 
transverse  diameter,  and  hence  would  cause  a  form  of 
double  vision,  in  spite  of  the  fact  that  they  would  keep  the 
visual  axes  in  the  normal  plane.  In  order  to  insure  binocular 
single  vision,  other  muscles  are  needed  besides  those  that 
govern  the  visual  axes ;  and  these  muscles  are  the  obliques. 
If  there  were  no  such  condition  as  astigmatism,  or  if  the 
principal  meridians  in  astigmatic  eyes  were  always  vertical 
and  horizontal,  there  would  be  but  one  function  for  the 
oblique  muscles,  and  that  function  would  be  the  keeping  of 
the  naturally  vertical  meridians  of  the  corneas  parallel,  and 
their  study  would  be  greatly  simplified.  The  prime  object 
of  this  paper,  however,  is  to  show  that  the  obliques  have 
another  and  more  complicated  function  to  perform  in  many 
cases.  Taking  causes  into  consideration,  we  may  say  that 
the  one  function  of  the  obliques  is  simple,  while  the  other  is 
complicated. 

The  Simple  Function  of  the  Obliques 
is  keeping  the  naturally  vertical   meridians   parallel.     The 
need  for  this  exists  in  all  eyes,  whatever  may  be  the  state  of 
refraction  other  than  oblique  astigmatism.     Even  in  oblique 


26  THE   FUNCTIONS   OF   THE  OBLIQUE   MUSCLES. 

astigmatism,  equal  in  amount  in  the  two  eyes  and  the  merid- 
ians of  greatest  curvature  being  parallel,  only  the  simple 
function  is  performed  by  the  obliques.  The  necessity  for 
this  function  of  the  obliques  resides  mainly  in  the  action  of 

The  Superior  and  Inferior  Recti, 
which  is  faulty  in  all  cases,  because  of  the  course  of  these 
muscles  and  their  attachment  to  the  globe.  When  the  in- 
ferior recti  are  called  upon  to  direct  the  visual  axes  below 
the  horizontal  plane  of  the  two  eyes,  they,  at  the  same  time, 
tend  both  to  converge  these  axes  and  to  rotate  the  eyes  so 
that  the  naturally  vertical  meridians  would  diverge  above. 
To  counteract  this  latter  tendency  the  superior  obliques  are 
thrown  into  a  state  of  activity,  and  the  parallelism  of  the  ver- 
tical meridians  is  maintained.  When  the  visual  lines  are  to 
be  directed  above  the  horizontal  plane,  by  contraction  of  the 
superior  recti,  these  muscles,  besides  tending  to  converge 
the  axes,  also  tend  to  converge  the  vertical  meridians  above, 
to  counteract  which  the  inferior  obliques  are  brought  into  a 
state  of  activity,  and  thus  parallelism  is  preserved. 

If  the  tendons  of  the  internal  and  external  recti  attach 
themselves  in  greater  part  below  the  horizontal  plane  of 
the  eye,  these  muscles,  in  adducting  and  abducting  the  eyes, 
would  tend  to  revolve  them  so  that  the  vertical  meridians  of 
the  corneas  would  diverge  above.  This  tendency  would  be 
counteracted  by  the  superior  obliques.  Should  the  lateral 
muscles  be  attached  to  the  globe  mainly  above  the  horizon- 


THE   FUNCTIONS   OF   THE  OBLIQUE   MUSCLES.  27 

tal  plane,  adduction  and  abduction  would  be  associated  with 
a  tendency  to  converge  the  vertical  meridians  above,  which 
would  be  prevented  by  the  action  of  the  inferior  obliques. 
It  is  probable  that  the  one  or  the  other  error  of  attachment 
of  the  internal  and  external  recti  is  not  uncommon. 

Thus  it  is  seen  that,  with  every  contraction  of  the  inferior 
recti,  there  must  be  an  associated  corrective  contraction  of 
the  superior  obliques ;  and  that,  with  every  action  of  the  supe- 
rior recti,  there  is  an  accompanying  and  correcting  action 
of  the  inferior  obliques.  Since  we  look  down  far  more 
than  we  look  up,  the  superior  oblique  muscles,  in  the  same 
proportion,  are  made  to  do  more  work  than  the  inferior 
obliques.  Thus  it  is  readily  seen  that  the  recti  and  oblique 
muscles,  while  opposing  one  another  in  action  to  a  certain 
extent,  work  together  in  effecting  binocular  single  vision, 
by  keeping  the  two  retinae  so  related  that  the  images  fall  on 
corresponding  parts. 

Plate  I.  represents  a  pair  of  eyes  that  are  non-astigmatic; 
or,  if  astigmatism  exists,  the  principal  meridians  are  vertical 
and  horizontal.  These  eyes  are  represented  as  looking  at  a 
rectangle.  The  line  ef  across  the  right  eye  is  the  horizon- 
tal meridian  and  the  line  gh  is  the  vertical  meridian,  while 
their  point  of  intersection  (5)  is  the  macula.  Similarly  the 
line  ej>  in  the  left  eye  represents  the  horizontal  nieridian, 
and  g/i  the  vertical  meridian,  their  point  of  intersection  (5) 
being  the  macula.     The  vertical  meridian  of  the  right  and 


THE   FUNCTIONS   OF  THE   OBLIQUE   MUSCLES.  2Q 

that  of  the  left  are  parallel.  Point  5  in  the  rectangle  is  the 
point  of  fixation.  The  line  5-5  from  the  macula  of  the  right 
eye  is  the  visual  axis  of  that  eye,  and  likewise  the  line  5-5 
is  the  visual  axis  of  the  left  eye.  These  intersect  at  point  5 
of  the  rectangle. 

According  to  the  well-known  law  of  refraction  by  curved 
surfaces,  such  as  are  now  under  consideration  (non-astig- 
matic eyes),  the  rectangular  object  will  throw  a  rectangular 
image  on  each  retina,  the  size  of  which  will  bear  a  definite 
proportion  to  the  size  of  the  object.  The  nodal  point  of  the 
right  eye  is  x,  through  which  all  lines  of  direction  from  this 
eye  must  pass.  The  lower  inner  corner  of  the  image  is  thus 
connected  with  the  upper  right-hand  corner  of  the  object  by 
the  line  1-1.  In  the  same  way  the  upper  inner  corner  of  the 
image  is  connected  with  the  lower  right-hand  corner  of  the 
object  by  the  visual  line  2-2  ;  and  so  on  for  the  other  corners  of 
image  and  object.  In  like  manner  the  corners  of  the  rectangu- 
lar image  in  the  left  eye  maybe  connected  with  corresponding 
corners  of  the  object  by  lines  passing  through  the  nodal 
point  (x)  of  that  eye.  If  the  left  eye  should  be  excluded,  the 
right  eye  would  see  the  rectangle  1-2-3-4;  ij:  tne  right  eye 
should  be  screened,  the  left  would  see  the  same  rectangular 
figure.  Both  eyes  together,  in  obedience  to  both  the  law  of 
corresponding  retinal  points  and  the  law  of  projection,  would 
see  the  one  common  rectangle  1-2-3-4.  The  superior  and  in- 
ferior recti  in  these  eyes  have  kept  the  visual  axes  in  the 


30  THE   FUNCTIONS   OF  THE  OBLIQUE   MUSCLES. 

normal  plane,  the  external  and  internal  recti  have  regulated 
their  tension  so  that  they  have  converged  these  axes  to  the 
point  5,  and  the  superior  and  inferior  obliques  have  kept  the 
naturally  vertical  meridians  parallel. 

It  has  already  been  stated  that  the  obliques  have  to  per- 
form only  the  simple  function  in  oblique  astigmatism,  when  the 
meridians  of  greatest  curvature  are  parallel  and  the  degree 
of  astigmatism  is  the  same  in  the  two  eyes ;  and  yet  it  would 
not  be  possible  for  such  eyes  to  see  the  rectangle  held  in  the 
position  shown  in  Plate  I.  as  a  rectangle.  Let  the  merid- 
ians of  greatest  curvature  be  at  45°  in  the  right  and  also 
at  450  in  the  left  eye.  As  a  result  of  the  refraction  of  the 
astigmatic  cornea  of  the  right  eye,  the  rectangular  figure 
would  throw  a  parallelogram  image  on  the  retina,  the  image 
inclining  down  and  out.  A  parallelogram  image  would  be 
thrown  on  the  left  retina  also,  and  it  would  incline  down  and 
in.  Looked  at  with  either  eye  alone,  the  rectangle  would 
be  seen  as  a  parallelogram  inclined  down  and  to  the  right; 
looked  at  with  both  eyes,  it  would  be  a  parallelogram  of  the 
same  shape  and  inclination  as  seen  by  each  eye  separately. 
The  extrinsic  muscles  of  these  eyes  have  performed  the 
same  function  as  the  muscles  of  the  eyes  shown  in  Plate  I., 
and  with  the  same  result — viz.,  binocular  single  vision.  The 
law  of  corresponding  retinal  points  and  the  law  of  projection 
having  full  sway  in  both  pairs  of  eyes,  the  one  pair  sees  the 
figure  as  it  is — a  rectangle — while  the  other  pair  sees  the 


THE   FUNCTIONS   OF   THE    OBLIQUE   MUSCLES.  3 1 

same  figure,  when  held  in  the  same  position,  as  a  parallelo- 
gram leaning  down  and  to  the  right.  With  the  visual  axes 
properly  directed  by  the  recti,  and  the  vertical  meridians 
kept  parallel  by  the  obliques,  the  two  eyes  are  kept  so  re- 
lated that  the  two  images  of  the  object  looked  at  fall  on  har- 
monizing parts  of  the  two  retinae,  and  the  object  is  neces- 
sarilv  seen  as  one,  and  of  the  same  shape  as  when  seen 
with  each  eye  separately. 

In  any  state  of  refraction  the  relationship  between  corre- 
sponding points  of  the  two  retinee  is  unalterable.  It  is  well 
known  that,  taken  as  a  whole,  the  nasal  half  of  one  retina 
harmonizes  with  the  temporal  half  of  the  other,  and  that  all 
points  of  either  retina  bear  a  fixed  and  unalterable  relation- 
ship to  the  macula  and  to  the  vertical  and  horizontal  merid- 
ians. A  retinal  point  in  the  nasal  half  of  the  right  retina, 
bearing  a  definite  relationship  to  the  macula  and  the  vertical 
and  horizontal  meridians,  must  harmonize  with  a  point  in  the 
temporal  half  of  the  left  retina  similarly  located ;  and  it  can 
harmonize  with  no  other  retinal  point  under  any  conditions. 

The  Complicated  Function  of  the  Obliques 
is  necessary  in  oblique  astigmatism  when  the  meridians  of 
greatest  curvature  diverge  or  converge  above.  This  is  neces- 
sary that  they  may  bring  harmonizing  parts  of  the  two  retinae 
under  dissimilar  images,  and  thus  insure  binocular  single 
vision;  but,  as  will  be  shown,  the  object,  though  seen  as 
one,  will  be  distorted. 


32  THE   FUNCTIONS    OF  THE   OBLIQUE   MUSCLES. 

Plate  II.  maybe  taken  for  study.  Both  eyes  have  oblique 
astigmatism  of  the  same  kind  and  quantity.  In  the  right 
eye  the  meridian  of  greatest  curvature  is  at  1350  and  in  the 
left  at  450.  As  set  forth  in  a  former  paper,  the  refraction 
in  oblique  astigmatism  is  such  as  to  make  vertical  and  hori- 
zontal lines  incline  toward  the  meridian  of  greatest  curva- 
ture. If  the  rectangular  figure  represented  in  Plate  I.  be 
held  in  the  same  position  before  the  eyes  represented  in 
Plate  II.,  it  would  not  be  seen  with  one  eye  alone  or  with 
both  together  as  a  rectangle.  The  rectangle  shown  in  Plate 
I.,  when  held  before  the  right  eye  in  Plate  II.,  instead  of 
throwing  a  rectangular,  would  throw  a  parallelogram  image 
on  the  retina.  The  same  rectangle  would  also  throw  a 
parallelogram  image  on  the  left  retina.  The  state  of  refrac- 
tion of  the  right  eye  would  make  the  distorted  image  lean 
down  and  toward  the  left,  while  the  distorted  image  in  the 
left  eye  would  lean  down  and  toward  the  right  side.  Cut- 
ting off  the  view  of  the  left  eye,  the  law  of  direction  would 
have  full  sway,  while  the  law  of  corresponding  points  would 
be  suspended.  Since  in  one  eye  alone  the  law  of  direction  is 
unalterable,  all  lines  of  direction  must  cross  in  the  center  of 
retinal  curvature;  and  the  right  eye,  with  the  parallelogram 
image  leaning  down  and  to  the  left,  must  see  the  figure  cast- 
ing the  image,  not  as  a  rectangle,  but  as  a  parallelogram 
leaning  down  and  to  the  left.  Screening  the  right  eye  while 
the  left  looks  on  the  rectangle,  it  is  seen,  not  as  a  rectangle, 


(33) 


34  THE  FUNCTIONS  OF  THE  OBLIQUE  MUSCLES. 

but  as  a  parallelogram  leaning  down  and  to  the  right,  the 
law  of  direction  determining  the  shape  of  the  figure  seen  by 
the  left  eye  just  as  it  fixed  the  shape  of  the  figure  seen  by 
the  right  eye.  Fig.  1-2-3-4  ^s  what  is  seen  with  the  right 
eye  alone;  fig.  i'-2'-^-^  is  what  is  seen  by  the  left  eye  alone. 
The  moment  these  two  eyes  are  allowed  to  look  at  the  rec- 
tangular figure,  the  law  of  corresponding  retinal  points  is 
brought  into  conflict  with  the  law  of  direction ;  and  the  lat- 
ter is  modified  by  the  former.  There  is  no  necessity  for 
changing  the  visual  axes  when  looking  at  the  rectangle  with 
these  two  eyes;  but,  unless  some  change  is  effected  in  some 
way,  each  eye  would  see  its  own  parallelogram  leaning  down 
and  toward  the  opposite  side.  Instantly  a  change  does  take 
place  in  both  eyes,  so  that  the  two  together  see,  not  a  rec- 
tangle nor  a  parallelogram,  but  a  trapezoid  with  the  longer 
side  above.  A  clear  understanding  of  what  this  change  is 
and  how  it  is  effected  may  be  had  by  a  further  study  of 
Plate  II.  In  the  right  eye  is  shown  a  dotted  parallelogram 
a-b-c-d,  of  precisely  the  same  form  as  the  parallelogram  im- 
age 1-2-3-4,  but  m  *he  former  the  upper  and  lower  lines  are 
parallel  with  the  horizontal  meridian.  In  the  left  eye  also 
is  shown  a  dotted  parallelogram  a'-b'-c'-d',  of  the  same  form  as 
the  parallelogram  i'-2'-3'-4',  with  its  upper  and  lower  lines 
parallel  with  the  horizontal  meridian  of  this  eye.  The  line 
c-d  in  the  right  eye  bears  throughout  the  same  relation  to  the 
macula,  the  horizontal  and  vertical  meridians  of  this  eye,  that 


THE   FUNCTIONS   OF   THE   OBLIQUE  MUSCLES.  35 

the  line  c'-b'  does  to  the  same  parts  of  the  left  eye,  and  there- 
fore correspond.  The  greater  part  of  the  line  d-a  in  the  right 
eye  also  corresponds  with  the  greater  part  of  the  line  d'-d  in 
the  left  eye,  the  parts  of  these  lines  not  corresponding  being 
their  extremities.  But  the  line  c-d  in  the  right  eye  nowhere 
corresponds  with  the  line  d-d'  in  the  left  except  at  the  points  of 
beginning  above ;  and  the  same  is  true  of  lines  b-a  and  b'-a\  in 
their  respective  eyes.  If  the  dotted  parallelograms  could  be 
made  to  coincide  with  the  parallelogram  images,  the  result 
would  be  that  the  two  eyes  together  would  see  the  figure 
a-b-c-d',  a  trapezoid  with  the  longer  side  above.  How  this 
is  effected  is  shown  in  Plate  III.,  where  each  eye  has  been 
revolved  on  its  visual  axis  by  the  superior  oblique  muscle, 
so  that  the  horizontal  meridian  is  made  parallel  with  the  up- 
per and  lower  borders  of  the  parallelogram  image ;  and  thus 
as  far  as  possible  corresponding  parts  of  the  two  retince  are 
brought  under  the  two  dissimilar  images,  and  the  figure  seen 
binocularly  is  a-b-c-d'.  The  part  of  this  trapezoid  seen  in 
common  by  the  two  eyes  is  a'-b-c-d,  the  part  seen  by  the 
right  alone  is  a-b-d ,  and  that  seen  by  the  left  eye  alone  is 
d-c-d '.  As  will  be  seen,  the  law  of  corresponding  points 
has  so  modified  the  law  of  projection  that  the  visual  lines  no 
longer  have  a  common  crossing  point.  This  is  anarchy,  so 
far  as  projection  is  concerned,  in  these  eyes. 

When  the  law  of  direction  is  interfered  with,  as  a  result  of 
the  conflict  between  it  and  the  more  imperious  law  of  corre- 


(36) 


THE   FUNCTIONS   OF  THE   OBLIQUE   MUSCLES.  37 

sponding  retinal  points,  the  object  seen  is  always  in  the  po- 
sition that  it  would  have  been  in,  had  the  images  primarily 
fallen  on  the  parts  of  the  two  retinas  that  have  been  rotated 
under  them  (by  either  the  recti  or  the  oblique  muscles)  in 
obedience  to  the  supreme  law  of  binocular  single  vision — 
the  law  of  corresponding  retinal  points.  The  displaced 
images,  as  a  result  of  either  natural  or  artificial  means,  cover 
areas  of  the  two  retinas  that  do  not  correspond.  In  order  to 
have  binocular  single  vision,  retinal  areas  that  do  correspond, 
and  are  of  same  shape  and  size  as  the  images,  must  be  brought 
under  them.  The  object  will  be  seen  as  though  no  rotation 
had  taken  place,  as  if  the  images  had  primarily  fallen  on 
these  parts,  in  perfect  obedience  to  the  law  of  projection, 
although  the  lines  of  direction  drawn  from  the  images  to  the 
single  object  will  not  cross  at  the  nodal  point.  In  cases  of 
decentration  of  the  maculas,  and  in  displaced  images  by 
means  of  prisms,  all  lines  of  direction  will  cross  at  one 
point,  but  that  point  will  be  above,  below,  to  the  outer  or 
inner  side  of  the  true  nodal  point;  while  in  oblique  astigma- 
tism, and  when  the  axes  of  correcting  cylinders  are  dis- 
placed, no  three  lines  of  direction  cross  at  the  same  point. 

In  like  manner  a  plate  could  be  made  showing  how  astig- 
matic eyes,  with  meridians  of  greatest  curvature  converging 
above,  would  see  a  rectangle  distorted  into  a  trapezoid,  the 
longer  side  below.  In  each  eye  there  would  be  a  parallelo- 
gram image  inclining  down  and  out.     To  fuse  these  into  a 


38  THE   FUNCTIONS    OF   THE   OBLIQUE   MUSCLES. 

trapezoid  the  inferior  oblique  muscles  would  be  brought  into 
action,  in  order,  as  far  as  possible,  to  bring  corresponding 
retinal  parts  under  dissimilar  images,  which  is  done  the 
moment  the  obliques  displace  the  horizontal  meridians,  so 
that  they  become  parallel  with  the  upper  and  lower  borders 
of  the  distorted  images. 

Imperfect  as  is  binocular  single  vision  in  uncorrected  ob- 
lique astigmatism,  the  meridians  of  greatest  curvature  either 
diverging  or  converging  above,  it  could  be  effected  in  no 
other  way  than  by  a  revolution  of  the  eyes  by  the  symmetric 
harmonious  action  of  the  oblique  muscles.  It  is  true  that 
nature  has  one  other  method  of  preventing  diplopia,  men- 
tal suppression  of  one  of  the  displaced  images.  It  may  be 
that  amblyopia  resulting  from  oblique  astigmatism  high  in 
degree,  and  from  insufficiency  of  the  obliques,  is  more  com- 
mon than  one  would  at  first  think.  Certainly,  if  the  ob- 
liques cannot  do  their  proper  work  in  effecting  binocular 
single  vision,  in  the  first  years  of  life,  nothing  is  more 
reasonable  than  to  suppose  that  amblyopia  ex  anopsia  would 
develop.  Who  has  not  seen  cases  of  amblyopia  without 
being  able  to  account  for  it? 

The  phenomena  outlined  in  this  paper  can  be  demonstrated 
experimentally  by  any  one  who  desires  to  prove  all  things ; 
for  he  can  produce  in  his  own  case,  at  pleasure,  any  form 
of  astigmatism.  But  some  may  be  ready  to  say  that  arti- 
ficial astigmatism  is    one    thing  and  natural  astigmatism  is 


THE   FUNCTIONS    OF  THE   OBLIQUE   MUSCLES.  39 

another  thing.  This  is  true,  but  only  in  name.  That  3  D. 
of  artificial  hypermetropic  astigmatism  is  the  same  error  of 
refraction  as  3  D.  of  natural  hypermetropic  astigmatism  is 
abundantly  proved  by  the  fact  that  each  is  thoroughly  cor- 
rected by  a  +  3  cylinder,  axis  properly  placed.  Either 
plus  or  minus  cylinders  may  be  used  in  the  experiments, 
for  the  one  is  as  capable  of  producing  artificial  astigmatism 
as  the  other;  if  the  plus  cylinders  (3.00  D.)  be  used,  the 
astigmatism  produced  has  its  meridian  of  greatest  curvature 
at  right  angles  to  the  axis  of  the  cylinder,  while  the  meridian 
of  greatest  curvature  would  correspond  with  the  axis  of  the 
minus  cylinders  (3.00  D.)  if  they  were  used. 

By  either  means  it  can  be  easily  proved  that  in  astigma- 
tism of  any  kind  (myopic,  hypermetropic,  or  mixed),  whose 
meridians  of  greatest  curvature  diverge  above,  there  is  a 
necessity  for  action  on  the  part  of  the  superior  oblique  mus- 
cles in  order  to  prevent  diplopia.  This  action,  having  its 
beginning  in  the  earliest  days  of  infancy  and  continuing 
during  waking  hours  until  the  cause  is  corrected  or  one  eye  is 
lost,  converges  the  naturally  vertical  meridians  above.  If 
the  meridians  of  greatest  curvature  converge  above,  the 
images  of  all  objects  are  so  displaced  in  the  two  eyes  as  to 
throw  into  activity  the  inferior  obliques,  so  that  diplopia  may 
be  prevented. 

In  astigmatism  with  the  principal  meridians  vertical  and 
horizontal,  the  only  eye  muscles  brought  into  action,  to  rem- 


40  THE    FUNCTIONS   OF   THE   OBLIQUE   MUSCLES. 

edy  in  any  way  the  condition,  are  the  ciliary  muscles.  In  ob- 
lique astigmatism  with  the  meridians  of  greatest  curvature 
diverging  above,  there  is  the  same  state  of  ciliary  strain  to 
sharpen  as  much  as  possible  the  images,  and  there  is  also  a 
necessary  activity  of  the  superior  obliques  so  as  to  bring 
corresponding  parts  of  the  two  retinae  under  the  oblique 
images,  that  there  may  be  binocular  single  vision.  Again,  in 
oblique  astigmatism  with  the  meridians  of  greatest  curvature 
converging  above,  there  is  the  ciliary  strain  for  sharpening 
the  images,  and  there  is  also  a  consequent  activity  of  the  infe- 
rior obliques  so  as  to  bring  similar  parts  of  the  retinae  under 
the  dissimilar  images,  resulting  in  binocular  single  vision. 

When  there  is  equality  of  strength  of  the  obliques  of  the 
two  eyes,  vertical  and  horizontal  astigmatism  will  give  less 
trouble  than  when  the  astigmatism  is  oblique  in  either  direc- 
tion, and  astigmatism  with  the  meridians  of  greatest  curvature 
diverging  above  need  give  no  more  annoyance  to  the  patient 
than  if  these  meridians  converged  above  when  the  plane  of 
vision  is  horizontal;  for,  in  the  former  case,  the  superior 
obliques  would  be  as  able  to  bear  the  strain  as  would  the 
inferior  obliques  in  the  latter  condition.  When  the  me- 
ridians of  greatest  curvature  diverge  above  and  the  plane  of 
vision  (visual  axes)  is  directed  down,  as  in  reading,  the 
added  strain  on  the  superior  obliques  would  give  more  an- 
noyance than  if,  in  the  same  patient,  the  meridians  of  great- 
est curvature  converged  above;  for  the  reason  that,  in  the 


THE   FUNCTIONS   OF   THE  OBLIQUE    MUSCLES.  4I 

latter,  the  simple  action  of  the  superior  obliques  to  overcome 
the  tendency  to  outward  rotation  of  the  eyes  by  the  inferior 
recti  would,  to  that  extent,  relieve  the  tension  of  the  inferior 
obliques  excited  by  the  astigmatism. 

But  the  obliques  are  not  always  harmonious.  The  supe- 
rior obliques  are  insufficient  in  at  least  25  per  cent,  of  all 
cases,  while  the  inferior  obliques  are  insufficient  in  less  than 
1  per  cent,  of  all  cases.  In  cases  of  insufficiency  of  the  su- 
perior obliques,  the  vertical  form  of  astigmatism  would  be 
worse  on  the  patient  than  if  he  had  oblique  astigmatism  with 
the  meridians  of  greatest  curvature  converging  above ;  and 
the  worst  form  of  astigmatism  would  be  that  in  which  the 
meridians  of  greatest  curvature  diverge  above.  The  reverse 
would  be  true  if  the  inferior  obliques  were  insufficient — a 
rare  condition. 

The  complicated  function  of  the  oblique  muscles  exists 
only  in  cases  of  oblique  astigmatism  with  meridians  of  great- 
est curvature  converging  or  diverging  above,  and  in  unequal 
degrees  of  oblique  astigmatism  when  the  meridians  of 
greatest  curvature  are  parallel.  The  necessity  for  this  func- 
tion is  entirely  destroyed  when  the  astigmatism  is  properly 
corrected;  but  the  action  of  the  obliques  does  not  always 
cease  at  once  in  binocular  single  vision  through  the  correct- 
ing cylinders.  The  old  habit  of  rotation  often  continues  for 
hours,  and  sometimes  for  days,  although  there  is  no  longer 
a  need  for  it,  and  the  result  is  metamorphopsia.     Inherent 


42  THE   FUNCTIONS    OF   THE   OBLIQUE   MUSCLES. 

weakness  of  the  superior  oblique  muscles,  in  a  large  per 
cent,  of  the  cases,  leads  to  a  more  speedy  disappearance  of 
the  metamorphopsia  when  the  meridians  of  greatest  curva- 
ture diverge  above  than  when  they  converge.  The  reverse 
would  be  true  in  a  case  of  insufficiency  of  the  inferior  ob- 
liques. The  habit  of  action  is  more  quickly  suspended  in 
a  weak  muscle  than  in  a  strong  one.  In  all  cases,  however, 
it  ceases,  and  the  metamorphopsia  vanishes,  under  the  con- 
tinuous wearing  of  the  correcting  cylinders. 

Artificial  conditions  may  excite  the  obliques  into  the  per- 
formance of  either  their  simple  or  complicated  function,  de- 
pending on  the  means  used.  A  prism  placed  base  up  be- 
fore one  eye  would  call  into  action  the  inferior  rectus  of 
that  eye.  This  action  would  tend  to  turn  the  vertical  merid- 
ian out  above,  which  tendency  would  be  at  once  counter- 
acted by  action  of  the  superior  oblique  so  as  to  keep  that 
meridian  parallel  with  the  vertical  meridian  of  the  fellow- 
eye.  A  prism,  with  base  up,  before  the  right  eye,  and  one 
with  base  down  before  the  left  would  call  into  action  the  in- 
ferior rectus  of  the  right  and  superior  rectus  of  the  left,  and 
there  would  be  an  associated  and  corrective  action  of  the  su- 
perior oblique  of  the  right  and  inferior  oblique  of  the  left,  if 
the  vertical  meridians  are  to  be  kept  vertical.  In  this  case, 
however,  the  naturally  vertical  meridians  being  still  parallel, 
though  not  vertical,  are  most  likely  allowed  to  remain  tilted, 
since  diplopia  would  not  result. 


THE   FUNCTIONS   OF   THE   OBLIQUE   MUSCLES.  43 

Prisms  placed  bases  out  before  the  eyes  will  call  into  ac- 
tion the  internal  recti  in  obedience  to  the  law  of  correspond- 
ing points.  If  these  muscles  are  attached  neither  too  high 
nor  too  low,  other  muscles  will  not  be  affected  by  the  prisms ; 
but  if  these  muscles  are  attached  too  low,  their  forced  action 
will  tend  to  make  the  naturally  vertical  meridians  diverge 
above,  when  a  corrective  action  of  the  superior  obliques  be- 
comes necessary;  or  if  the  attachment  is  too  high,  the  in- 
ferior obliques  act  to  prevent  the  convergence  of  the  verti- 
cal meridians  above.  The  indirect  effect,  on  the  oblique 
muscles,  of  prisms  in  position  of  rest  for  weak  recti  muscles, 
may  account  largely  for  the  unsatisfactory  results  of  that 
once  common  plan  of  treatment. 

In  the  rhythmic  exercise  treatment  of  the  internal  recti 
muscles,  a  state  of  insufficiency  of  the  superior  obliques  is 
sometimes  developed  that  was  not  manifest  in  the  beginning 
even  under  the  proof  tests.  The  only  explanation  is  that  the 
internal  recti  in  these  cases  are  attached  too  high,  and  their 
exercise  has  been  necessarily  associated  with  corrective 
rhythmic  action  of  the  inferior  obliques,  so  that  they  become 
too  strong  for  the  superior  obliques.  These  cases  do  not 
improve  as  they  should,  until  proper  attention  is  given  to  the 
superior  obliques.  In  only  two  instances  have  I  seen  insuf- 
ficiency of  the  inferior  obliques  develop  as  a  result  of  exer- 
cise of  the  interni ;  and  it  is  easy  to  suppose  that  in  these 
cases  the  interni  were  attached  too  low,  and  that  consequent- 


44  THE   FUNCTIONS   OF  THE   OBLIQUE   MUSCLES. 

ly  their  exercise  was  associated  with  corrective  rhythmic  con- 
traction of  the  superior  obliques,  resulting  in  their  hyperde- 
velopment.  These  cases  did  not  do  well  until  attention  was 
given  to  the  inferior  obliques  in  connection  with  the  treat- 
ment of  the  interni. 

The  effect  of  prisms  on  the  externi,  under  conditions  of 
too  high  or  too  low  attachment,  would  bring  about  a  second- 
ary effect  on  the  obliques,  precisely  as  has  been  described 
in  connection  with  the  interni.  In  either  case  the  obliques 
are  performing  their  simple  function,  that  of  keeping  the 
naturally  vertical  meridians  parallel. 

The  complicated  function  of  the  obliques  may  be  excited 
by  artificial  means  also.  As  already  stated,  artificial  ob- 
lique astigmatism  calls  into  harmonious  symmetric  activity 
either  the  superior  or  inferior  obliques,  depending  on  the 
divergence  or  convergence  above  of  the  meridians  of  great- 
est curvature. 

In  the  correction  of  anv  form  of  astigmatism,  the  proper 
location  for  the  axes  of  the  cylinders  should  always  be  de- 
termined, as  a  variation  in  either  direction  would  throw 
strain  on  the  oblique  muscles,  which  would  be  badly  borne 
in  proportion  to  the  strength  of  the  displaced  cylinders  and 
the  extent  of  their  deviation.  Several  curious  facts  may  be 
brought  forward  here,  and  reasons  can  be  given  why  advan- 
tage should  be  temporarily  taken  of  these  facts  in  certain 
cases.     Fig.  i,  in  Plate  IV.,  represents  a  pair  of  hyperme- 


Right 


Left 


F/s-t 


Fij.  2 


Fij  3 


FiJ-  4 

Plate  IV 


(45) 


46  THE   FUNCTIONS    OF   THE   OBLIQUE   MUSCLES. 

tropic  astigmatic  eyes,  the  meridians  of  greatest  curvature 
being  vertical  in  each  eye.  The  plus  cylinders,  axes  900 
(«),  insure  against  strain  of  either  the  superior  or  inferior 
obliques;  but  let  the  glasses  be  turned  in  their  rims  so  that 
the  axis  of  the  right  shall  stand  at  8o°  (£)  and  the  axis  of 
the  left  at  ioo°  (/;),  images  will  be  distorted,  as  shown  in 
Plate  II.,  which  would  necessitate  strain  on  the  part  of  the 
superior  oblique  muscles.  The  distortion  of  the  images 
would  increase,  and  the  strain  on  the  superior  obliques 
would  be  greater,  as  the  axes  are  revolved  farther  away 
from  the  vertical,  the  maximum  being  reached  at  450  (c)  for 
the  right,  and  135  (c)  for  the  left  eye.  Passing  these  points 
the  distortion  grows  less,  until  at  180°  (d)  for  each  eye  it  dis- 
appears. 

Fig.  2  represents  the  same  pair  of  eyes.  If  now  the  axis 
of  the  right  cylinder  should  be  revolved  from  900  (a)  to 
ioo°  (l>)  and  that  of  the  left  from  900  (a)  to  8o°  (£),  the 
distortion  of  images  would  be  such  as  to  call  into  activity 
the  inferior  obliques,  so  that  there  might  be  binocular 
single  vision.  This  distortion  would  reach  its  maximum 
when  the  axis  of  the  right  cylinder  stands  at  135°  (c)  and 
that  of  the  left  at  450  (c),  again  lessening  as  the  axes  are 
made  to  approach  the  horizontal,  where  the  distortion  ceases. 

Fig.  3,  Plate  IV.,  represents  a  pair  of  hypermetropic  astig- 
matic eyes  with  the  meridian  of  greatest  curvature  for  the 
right  at  700  (a)   and  that  of  the  left  at  no°  (a).     (In  all 


THE   FUNCTIONS    OF   THE   OBLIQUE   MUSCLES.  47 

the  figures  of  plates  IV.,  V.,  and  VI.,  the  mark  within  the 
circle  shows  the  location  of  the  meridian  of  greatest  curva- 
ture.) These  meridians  converging  above  would  cause 
strain  on  the  inferior  obliques,  which  would  be  relieved  by 
the  correcting  cylinders,  axis  of  the  right  at  700  (a)  and  of 
the  left  at  no°  (a).  A  revolution  of  the  axis  of  the  right 
cylinder  to  450  (b)  and  that  of  the  left  to  1350  (b)  would 
so  displace  the  images  as  to  call  into  action  the  superior 
obliques,  the  displacement  increasing  as  the  axes  are 
moved  until  these  points  (b  for  each  eye)  are  reached. 
Continuing  the  revolution  of  the  cylinders  in  the  same  di- 
rections, the  displacement  lessens,  and  disappears  entirely 
when  the  axis  of  the  right  reaches  200  (c)  and  that  of 
the  left  1600  (c);  and  the  necessity  for  action  of  the  ob- 
liques no  longer  exists.  If  the  axes  of  the  cylinders  are 
moved  from  their  correct  positions  (700  for  the  right  and 
uo°  for  the  left  eye)  to  900  (/")  for  each  eye,  images  will 
be  so  displaced  as  to  call  into  corrective  activity  the  inferior 
obliques.  The  maximum  of  displacement  would  be  effected 
when  the  axis  reaches  1350  (e)  in  the  right  and  450  (c)  in 
the  left  eye.  Continuing  the  revolution  in  the  same  direc- 
tions, the  displacement  would  grow  less,  and  finally  disap- 
pear when  the  axis  of  the  right  stands  at  d,  and  that  of  the 
left  at  d,  each  200  above  the  horizontal.  As  will  be  seen, 
the  arc  of  distortion,  so  as  to  throw  strain  on  the  superior 
obliques,  is  500  (from  700  to  200  in  the  right  eye,  and  from 


4b  THE   FUNCTIONS    OF   THE   OBLIQUE   MUSCLES. 

no°  to  i6o°  in  the  left  eye),  while  the  arc  of  distortion  that 
would  throw  strain  on  the  inferior  obliques  is  1300  (from  a 
to  d). 

Fig.  4,  Plate  IV.,  shows  the  meridians  of  greatest  curva- 
ture of  these  hypermetropic  astigmatic  eyes  at  no°  (a)  for 
the  right  and  700  (a)  for  the  left.  These  meridians  di- 
verging above,  would  call  into  corrective  activity  the  supe- 
rior oblique  muscles.  Correctly  chosen  and  properly  placed 
cylinders,  by  correcting  the  distortion  of  the  images,  would 
remove  the  necessity  for  the  performance  of  the  complicated 
function  of  the  superior  obliques.  Displacing  the  axes  of 
these  cylinders,  the  right  to  1350  (b)  and  the  left  to  450  (3), 
would  cause  a  maximum  of  distortion  of  the  images,  of  the 
kind  to  call  into  action  the  inferior  obliques.  Continuing 
the  revolution  of  the  cylinders,  the  distortion  would  disap- 
pear when  the  axis  of  the  right  reaches  1600  (c)  and  that  of 
the  left  200  (c).  Should  the  axes  of  the  cylinders  be  revolved 
from  their  proper  places — at  no°  (a)  in  the  right  and  700 
(a)  in  the  left — to  900  (/")  for  each  eye,  the  images  would  be 
so  changed  as  to  call  into  harmonious  activity  the  superior 
obliques.  The  maximum  distortion  would  occur  when  the 
axis  of  the  right  is  at  45 °  (e)  and  that  of  the  left  at  1350  (<?). 
Continuing  the  revolution,  the  distortion  would  disappear 
when  the  axes  reach  the  points  d  above  the  horizontal 
meridians.  In  this  case  the  arc  of  distortion  causing  activ- 
ity of  the  inferior  obliques  is  500  (from  a  to  c)  while  the 


THE   FUNCTIONS   OF   THE    OBLIQUE   MUSCLES.  49 

arc  of  distortion  that  would  throw  strain  on  the  superior  ob- 
liques is  1300  (from  a  to  d).  If  in  this  pair  of  eyes  the  me- 
ridians of  greatest  curvature  had  been  at  1300  for  the  right 
and  50°  degrees  for  the  left,  the  arc  of  distortion  that 
would  call  the  inferior  obliques  into  action  would  be  only 
io°,  while  the  one  that  would  cause  activity  of  the  superior 
obliques  would  be  1700  (1800  less  io°). 

Fig.  1,  Plate  V.,  represents  hypermetropic  astigmatic 
eyes,  the  meridians  of  greatest  curvature  being  at  1800  («) 
in  each  eye,  a  condition  that,  in  itself,  would  not  call  either 
the  superior  or  inferior  obliques  into  activity.  The  correct 
plus  cylinders,  axes  1800,  would  sharpen  the  blurred  but 
not  distorted  images.  Displacing  these  axes  in  the  lower 
temporal  quadrants  would  so  distort  the  images  as  to  throw 
into  action  the  superior  obliques ;  and  the  maximum  of  dis- 
tortion would  be  effected  when  the  axes  reached  450  (c)  in 
the  right  and  1350  (c)  in  the  left  eye.  With  the  axes  turned 
to  900  (d)  there  would  be  no  distortion  of  images,  though 
there  would  be  blurring,  as  in  all  cases  of  displaced  cyl- 
inders. 

Fig.  2,  Plate  V.,  represents  the  same  pair  of  eyes  shown 
in  Fig.  1.  The  axes  of  the  correcting  cylinders  revolved  in 
the  lower  nasal  quadrant  would  so  distort  images  as  to  call 
into  action  the  inferior  oblique  muscles,  the  maximum  being 
effected  when  the  axes  stand  at  1350  (c)  for  the  right  and 
450  (c)  for  the  left  eye,  the  distortion  lessening  as  the  axes 


Ricnr 


Urr 


F,j.l 


.  r\ 


Fig.  2 


F,j  3 


d     c 


(50) 


Fij.  + 

Plate  V. 


THE   FUNCTIONS   OF   THE  OBLIQUE   MUSCLES.  5 1 

approach,  and  disappearing  altogether  when  they  reach 
900  (d). 

A  comparative  study  of  Figs,  i  and  2  of  Plate  IV.,  with 
Figs,  i  and  2  of  Plate  V.,  will  show  that  in  hypermetropic 
astigmatism  with  the  meridians  of  greatest  curvature  either 
vertical  or  horizontal,  a  revolution  of  the  axes  of  the  cylin- 
ders in  the  lower  temporal  quadrant  will  distort  images  (as 
of  a  rectangle)  down  and  in,  and  thus  will  call  into  harmo- 
nious action  the  superior  obliques;  and  it  will  also  show 
that  a  revolution  of  the  cylinders  in  the  lower  nasal  quad- 
rants will  so  displace  the  images  as  to  call  into  harmonious 
action  the  inferior  obliques. 

Fig.  3,  Plate  V.,  represents  a  pair  of  hypermetropic  astig- 
matic eyes  with  the  meridian  of  greatest  curvature  for  the 
right  eye  at  200  (a)  and  that  of  the  left  at  1600  (a).  Since 
these  meridians  converge  above,  the  uncorrected  condition 
would  cause  harmonious  action  of  the  inferior  obliques. 
Properly  chosen  and  correctly  placed  cylinders,  axes  at  200 

(a)  for  the  right  and  1600  (a)  for  the  left  eye,  would  re- 
lieve the  distortion  of  the  images  and  do  away  with  the  ne- 
cessity for  the  complicated  function  of  the  obliques.  Re- 
volving the  axis  of  the  right  cylinder  from  200  (a)  to  45 ° 

(b)  and  that  of  the  left  from  1600  (a)  to  1350  (&)  would 
cause  a  maximum  displacement  of  images  in  such  a  way 
as  to  call  into  action  the  superior  oblique  muscles,  the 
distortion    disappearing    when    these    axes  reach    700    (c) 


52  THE   FUNCTIONS   OF  THE   OBLIQUE   MUSCLES. 

for  the  right  and  no°  (c)  for  the  left  eye.  Passing  700 
(c)  in  the  right  and  no°  (c)  in  the  left,  the  distortion  be- 
comes reversed,  so  that  the  strain  will  be  thrown  on  the 
inferior  obliques,  the  maximum  being  attained  when  the 
axis  of  the  right  stands  at  1350  (e)  and  that  of  the  left  at 
45°  (c).  The  distortion  decreases  as  the  axes  are  still  far- 
ther turned  in  the  same  directions,  and  disappears  at  the  end 
of  the  arc  of  130°  (from  c  to  f)  when  they  coincide  with 
the  meridians  of  greatest  curvature.  Thus  the  arc  of  dis- 
tortion involving  the  superior  obliques  is  500  (from  a  to  c) 
while  that  involving  the  inferior  obliques  is  1300  (from 
ctof). 

The  eyes  (hypermetropic  astigmatic)  represented  by  Fig. 
4,  Plate  V.,  have  their  meridians  of  greatest  curvature  at 
1600  (a)  in  the  right  and  200  (a)  in  the  left.  These  me- 
ridians diverging  above  would  result,  in  the  uncorrected 
case,  in  calling  into  harmonious  action  the  superior  ob- 
liques. Proper  cylinders  with  the  axis  of  the  right  at  160° 
(a)  and  that  of  the  left  at  200  (a)  would  correct  the  dis- 
tortion of  the  images,  and  relieve  the  strain  on  the  superior 
obliques.  A  turning  of  these  cylinders  in  the  arcs  a-c 
would  distort  the  retinal  images  so  as  to  bring  into  action 
the  inferior  oblique  muscles,  the  maximum  distortion  exist- 
ing when  the  axes  are  at  b.  Continuing  the  revolution  from 
c,  the  distortion  becomes  reversed,  and  as  a  consequence  the 
superior  obliques  are    brought  into    activity,  the  maximum 


THE   FUNCTIONS   OF   THE   OBLIQUE   MUSCLES.  53 

being  attained  when  the  axes  reach  e.  As  the  axes  are  re- 
volved farther  the  distortion  lessens,  and  finally  disappears 
when  they  stand  aty,  again  coinciding  with  the  meridians  of 
greatest  curvature.  In  this  pair  of  eyes  the  arc  of  distortion 
involving  the  inferior  obliques  is  500  (from  a  to  c),  while 
that  involving  the  superior  obliques  is  130°,  the  maximum  of 
distortion  in  both  instances  being  attained"  when  the  halfway 
point  of  the  arc  is  reached  by  the  axis  of  the  cylinder. 

A  comparative  study  of  any  two,  or  of  all  the  figures  in 
Plates  IV.  and  V.  will  show  that  the  arc  of  distortion,  by 
corrective  plus  cylinders,  involving  the  superior  obliques,  is 
always  in  the  lower  temporal  quadrant  wholly  or  in  greater 
part;  and  if  entirely  within  this  quadrant,  its  length  is  al- 
ways twice  the  distance  from  the  meridian  of  greatest  curva- 
ture to  the  450  point  of  the  quadrant,  the  other  half  being 
on  the  opposite  side  of  the  latter.  In  like  manner  it  will  be 
seen  that  the  arc  of  distortion  involving  the  inferior  obliques, 
by  a  revolution  of  plus  cylinders,  is  always  in  the  lower  nasal 
quadrant  wholly  or  in  greater  part;  and  if  entirely  within  the 
quadrant,  its  length  is  twice  the  distance  from  the  meridian 
of  greatest  curvature  to  the  450  point  of  the  quadrant,  the 
other  half  being  on  the  opposite  side  of  the  latter.  When 
the  arc  of  distortion  involving  the  superior  obliques  is  900, 
that  involving  the  inferior  obliques  is  900,  and  vice  versa. 
When  the  arc  of  distortion  involving  the  superior  obliques  is 
less  than  900,  the  arc  involving  the  inferior  obliques  is  al- 


54  THE   FUNCTIONS    OF   THE   OBLIQUE   MUSCLES. 

ways  the  difference  between  the  former  and  1800,  and  vice 
versa.  The  maximum  of  distortion  is  always  attained 
when  the  axis  of  the  cylinder  is  at  the  halfway  point  of 
the  arc. 

Fig.  i,  Plate  VI.,  represents  a  pair  of  hypermetropic  as- 
tigmatic eyes,  the  meridian  of  greatest  curvature  of  the 
right  at  450  (a)  and  that  of  the  left  at  1350  (a).  These  me- 
ridians converging  above  would  cause  such  distortion  of  im- 
ages as  to  throw  into  harmonious  action  the  inferior  oblique 
muscles.  The  proper  cylinders,  correctly  placed — axis  of 
the  right  at  45 °  (a)  and  the  axis  of  the  left  at  1350  (a) — 
would  counteract  the  distortion,  and  relieve  the  inferior  ob- 
liques of  the  necessity  of  acting.  Revolving  the  axes  of  the 
correcting  cylinders  in  either  direction  would  so  distort  im- 
ages as  to  call  into  harmonious  action  the  inferior  oblique 
muscles.  Since  the  arc  of  distortion  for  the  superior  ob- 
liques in  this  case  is  nothing,  the  arc  of  distortion  for  the 
inferior  obliques  is  1800,  from  a  to  d  in  either  direction,  the 
maximum  of  distortion  being  attained  respectively  at  e  above 
and  at  c  below. 

Fig.  2,  Plate  VI.,  represents  a  pair  of  the  same  kind  of 
eyes,  but  with  the  meridian  of  greatest  curvature  at  135° 
(a)  for  the  right  and  450  (a)  for  the  left.  These  meridians 
diverging  above,  the  refraction  is  such  as  to  distort  images 
so  as  to  call  into  harmonious  action  the  superior  obliques. 
As  in  the  other  case,  the  correct  cylinders,  properly  placed, 


THE  FUNCTIONS   OF  THE   OBLIQUE   MUSCLES. 


55 


counteract  the  distortion,  and  relieve  the  superior  obliques 
from  action.  Rotating  the  axes  of  these  cylinders  in  either 
direction  from  a  would  so  distort  images  as  to  call  into  ac- 
tivity the  superior  obliques.  In  this  case  the  arc  of  distor- 
tion for  the  inferior  obliques  is  nothing,  and  therefore  the 


Rl&HT 


Left 


fay  1 


Plate  71 
arc  of  distortion  for  the  superior  obliques  is  i8o°,  from  a  to 
d  in  either  direction,  the  maximum  being  attained  at  c  above 
and  e  below. 

A  careful  study  of  Plates  IV.,  V.,  and  VI.  is  fraught  with 
practical  importance.  In  all  cases  the  exact  location  of  the 
meridian  of  the  best  (greatest  in  hypermetropic  astigma- 
tism) curvature  should  be  sought  for  with  the  greatest  care, 


56  THE   FUNCTIONS    OF   THE   OBLIQUE   MUSCLES. 

and  may  always  be  found;  and  the  lens  should  be  cut  so 
that  its  axis  may  coincide  with  this  meridian,  although,  as 
will  be  shown  farther  on,  it  may  not  always  be  best  so  to 
place  it  at  first  in  the  frames.  Based  on  the  teachings  of 
my  paper  on  the  "Harmonious  Symmetric  Action  of  the 
Oblique  Muscles  in  Oblique  Astigmatism,"  published  more 
than  three  years  ago,  Dr.  N.  C.  Steele,  of  Chattanooga, 
Tenn.,  U.  S.  A.,  formulated  a  perfect  working  rule  for  de- 
termining the  position  of  the  best  meridian  in  hypermetropic 
astigmatism,  there  being  in  the  given  case  no  insufficiency  of 
the  oblique  muscles.  The  fellow-eye  being  covered,  the 
eye  under  examination,  no  longer  being  dominated  by  the 
law  of  corresponding  points,  is  likely  at  times  to  roll  into 
the  easy  position  (naturally  vertical  meridian  becoming  ver- 
tical) by  a  relaxation  of  the  muscles  accustomed  to  over- 
acting in  binocular  single  vision.  This,  of  course,  would 
cause  the  meridian  of  greatest  curvature  to  slightly  vary  its 
position,  the  variation  being  in  proportion  to  the  amount  of 
obliquity  of  the  astigmatism  and  the  quantity,  but  rarely,  if 
ever,  amounting  to  more  than  50.  If  the  best  meridian  is  in 
the  lower  temporal  quadrant,  and  there  is  doubt  between 
two  points  50  apart,  the  axis  of  the  plus  cylinder  should  be 
placed  at  the  higher;  if  the  best  meridian  is  in  the  lower 
nasal  quadrant,  and  there  is  doubt  between  two  points  50 
apart,  the  axis  of  the  plus  cylinder  should  likewise  be  placed 
at  the  higher  point.     Steele's  rule  in  all  cases  of  oblique  hy- 


THE   FUNCTIONS   OF   THE    OBLIQUE   MUSCLES.  57 

permetropic  astigmatism  is:  "In  those  cases  in  which  the 
axes  of  the  proper  cylinders  for  the  two  eyes  diverge  above, 
place  the  c}'linders  at  those  points  which  will  give  the  axes 
the  greatest  divergence  permitted  by  the  tests ;  and  in  those 
cases  in  which  the  axes  converge  above,  place  them  at  the 
points  which  will  give  them  the  greatest  convergence  per- 
mitted by  the  tests." 

While  the  above  rule,  in  cases  free  from  insufficiencv  of 
the  oblique  muscles,  is  a  perfect  one,  so  far  as  finding  how 
the  lenses  should  be  cut  is  concerned,  it  is  not,  even  in 
these  cases,  the  rule  to  be  followed  in  the  immediate  plac- 
ing of  the  lenses  in  the  frames.  After  a  time,  however,  the 
cylinders  cut  according  to  the  Steele  rule  should  be  so  placed 
permanently. 

In  the  case  represented  by  Fig.  3,  Plate  IV.,  since  the 
meridians  of  greatest  curvature  converge  above,  the  inferior 
obliques  have  always  been  accustomed  to  overacting,  while 
the  superior  obliques,  to  the  same  extent,  have  been  accus- 
tomed to  doing  less  work  than  would  have  been  required  of 
them  in  eyes  free  from  oblique  astigmatism.  Placing  the 
axis  of  the  right  cylinder  at  700  (a)  and  that  of  the  left  at 
no°  (a)  would  at  once  take  away  the  cause  for  overaction  on 
the  part  of  the  inferior  obliques.  The  necessity  for  work  so 
suddenly  taken  from  them  is  just  as  quickly  transferred  to  the 
superior  obliques,  and  as  a  result,  in  most  cases,  either  there 
is  suffering  excited,  the  superior  obliques  responding  to  the 


58  THE   FUNCTIONS    OF  THE   OBLIQUE   MUSCLES. 

new  demand,  or  there  is  metamorphopsia,  these  muscles  re- 
belling for  the  time  against  the  new  conditions  brought  about 
by  the  cylinders.  Both  the  suffering  and  the  metamorphop- 
sia may  be  avoided  by  revolving  the  cylinders  in  the  rims, 
so  that  their  axes  are  made  to  traverse  the  arc  (a-d)  of  dis- 
tortion for  the  inferior  obliques  to  the  extent  of  50  to  io°. 
The  distortion  will  create  the  necessity  for  action  on  the 
part  of  the  inferior  obliques  of  the  kind  to  which  they  have 
always  been  accustomed.  Since  the  cylinders  are  made  to 
describe  larger  arcs  than  the  meridians  of  greatest  curvature 
are  made  to  traverse  by  the  action  of  the  inferior  obliques, 
there  will  not  be  coincidence  of  the  axes  of  the  cylinders 
and  meridians  of  greatest  curvature  ;  and  vision  to  that  extent 
will  be  blurred,  though  sharper  than  if  no  cylinders  were 
on.  Beginning  with  the  cylinders  thus  displaced,  they 
should  be  revolved  i°  or  2°,  every  second  or  third  da}', 
back  toward  the  equilibrium  positions  of  the  meridians  of 
best  curvature.  Each  backward  move  will  take  away  part 
of  the  necessity  for  work  from  the  inferior  obliques,  trans- 
ferring the  same  quantity  of  work  to  the  superiors.  Thus  by 
degrees  the  work  is  transferred  from  the  inferior  obliques 
to  the  superiors,  and  that,  too,  without  exciting  either  dis- 
comfort or  metamorphopsia.  In  this  case  it  would  be  a  se- 
rious mistake  to  displace  the  axes  in  the  arc  (a-b)  of  distor- 
tortion  for  the  superior  obliques ;  for,  to  the  work  trans- 
ferred   from   the    inferior   to    the    superior  obliques,  there 


THE   FUNCTIONS   OF   THE   OBLIQUE   MUSCLES.  59 

would  be  added  the  contraction  necessary  to  harmonize  the 
distorted  images. 

In  like  manner  it  could  be  shown  that  the  axes  of  the  cyl- 
inders for  correcting  the  astigmatism  represented  in  Fig.  4, 
Plate  IV.,  should  be  temporarily  placed  50  or  io°  from  their 
permanent  places  in  the  arcs  (a-d)  of  distortion  for  the  su- 
perior obliques.  As  in  the  case  represented  in  Fig.  3,  Plate 
IV.,  the  axes  should  be  gradually  revolved  back  to  their 
permanent  resting  place. 

In  any  case  of  oblique  astigmatism  with  meridians  of 
greatest  curvature  converging  above  (see  Fig.  3,  Plate  IV.; 
Fig.  3,  Plate  V. ;  and  Fig.  1,  Plate  VI.),  there  being  no  in- 
sufficiency of  the  inferior  obliques,  the  axes  of  correcting 
cylinders  should  be  temporarily  displaced  50  or  more  within 
the  arcs  of  distortion  for  the  inferior  obliques,  and  gradual- 
ly revolved  back  to  their  proper  permanent  points.  Since 
there  is  no  arc  of  distortion  for  the  superior  obliques  in  the 
eyes  shown  in  Fig.  1,  Plate  VI.,  the  temporary  displacement 
may  be  either  up  or  down  from  a. 

In  any  case  of  oblique  astigmatism,  with  meridians  of 
greatest  curvature  diverging  above  (see  Fig.  4,  Plate  IV.; 
Fig.  4,  Plate  V. ;  and  Fig  2,  Plate  VI.),  there  being  no  in- 
sufficiency of  the  superior  obliques,  the  axes  of  the  cor- 
recting cylinders  should  be  temporarily  displaced  50  or 
more  in  the  arcs  of  distortion  for  the  superior  obliques,  the 
backward  change  being  effected  by  degrees,  so  as  to  grad- 


60  THE   FUNCTIONS    OF   THE   OBLIQUE   MUSCLES. 

ually  transfer  work  from  one  muscle  to  the  other.  Since 
there  is  no  arc  of  distortion  for  the  inferior  obliques  in 
the  eyes  shown  in  Fig.  2,  Plate  VI.,  the  temporary  dis- 
placement of  the  axes  may  be  either  above  or  below  the 
points  a. 

So  far,  in  speaking  of  the  arcs  of  distortion  for  oblique 
muscles,  plus  cylinders  have  been  in  mind.  When  minus 
cylinders  are  required,  what  would  be  the  arc  of  distortion 
for  the  superior  obliques,  if  plus  cylinders  were  used,  be- 
comes the  arc  of  distortion  for  the  inferior  obliques,  and 
vice  versa. 

Unfortunately  tnere  is  not  always  perfect  equilibrium  of 
the  oblique  muscles  in  oblique  astigmatic  cases.  If,  as  is 
most  common,  there  is  insufficiency  of  the  superior  obliques, 
oblique  astigmatism  with  meridians  of  greatest  curvature 
converging  above  will  give  but  little  trouble,  as  compared 
with  astigmatism  in  which  these  meridians  diverge  above; 
and  for  the  very  good  reason  that  in  the  former  there  is  har- 
monious strain  on  the  strong  inferior  obliques,  while  in  the 
latter  there  is  harmonious  strain  on  the  weak  superior  ob- 
liques. 

Uncorrected  oblique  astigmatism  with  meridians  of  great- 
est curvature  converging  above,  associated  with  insufficiency 
of  the  superior  oblique  muscles,  is  far  more  endurable  than 
is  the  most  perfect  correction  of  the  astigmatic  error  that 
can  be  made,  when  the  insufficiency  itself  is  ignored.     On 


THE   FUNCTIONS    OF  THE   OBLIQUE   MUSCLES.  6 1 

the  other  hand,  when  insufficiency  of  the  superior  obliques 
complicates  oblique  astigmatism  with  the  meridians  of  great- 
est curvature  diverging  above,  the  correcting  cylinders  give 
immediate  relief,  and  become  a  joy  forever. 

If  it  is  important  in  cases  of  oblique  astigmatism,  not  as- 
sociated with  insufficiency  of  the  superior  obliques,  to  dis- 
place temporarily  the  axes  of  the  cylinders  in  the  arcs  of  dis- 
tortion for  the  inferior  obliques,  it  becomes  doubly  necessa- 
ry to  do  so  when  there  is  insufficiency  of  the  superior  ob- 
liques as  a  complication ;  and  if  these  axes  are  ever  to  be  re- 
volved back,  so  that  they  shall  coincide  with  the  proper  prin- 
cipal meridians,  the  weak  obliques  must  be  first  developed  by 
exercise. 

There  is  another,  and  very  proper  method  of  correcting 
oblique  astigmatism,  especially  that  form  in  which  the  me- 
ridians of  greatest  curvature  converge  above.  As  already 
pointed  out,  the  distortion  of  images  (meridians  of  greatest 
curvature  converging)  is  such  as  to  throw  work. on  the  in- 
ferior oblique  muscles.  A  partial  (say  one-fourth)  correc- 
tion of  the  astigmatism  will  slightly  relieve  the  distortion  of 
the  images,  and  will  thus  transfer  one-fourth  of  the  work 
from  the  inferior  obliques  to  the  superior  obliques.  Having 
used  the  quarter  correction  for  a  few  days,  a  half  correction 
might  be  given,  when  another  fourth  of  the  distortion  of 
images  is  relieved,  and  a  proportionate  amount  of  work 
is  again  transferred  from  the  inferior  to  the  superior  ob- 


62  THE   FUNCTIONS   OF  THE   OBLIQUE  MUSCLES. 

liques.  After  another  period  of  a  few  days,  a  three-quarter 
correction  could  be  given;  and  so  on  to  the  full  correction, 
thus  gradually  giving  the  patient  full  acuity  of  vision,  and  as 
gradually  transferring  work  from  the  inferior  to  the  superior 
obliques. 


CHAPTER  III. 

THE  OBLIQUE  MUSCLES  AS  RELATED  TO  OB- 
LIQUE ASTIGMATISM:  REPLY  TO  DR.  HOTZ'S 
CRITICISM*  

Mr.  Editor:  With  your  kind  permission,  I  will  occupy  a 
part  of  your  space  in  answering  the  criticism  of  my  views  on 
the  action  of  the  oblique  muscles  in  oblique  astigmatism,  as 
published  by  Dr.  F.  C.  Hotz,  in  your  last  issue.  Allow 
me  first  to  plead  guilty  to  the  charge  of  having  "talked" 
much,  and  "written"  more,  on  this  subject.  I  plead  guilty, 
further,  to  the  charge  of  having  taught  one  thing  (harmo- 
nious non-symmetric  action)  in  1887  and  another  thing 
(harmonious  symmetric  action)  in  T891.  To  have  taught 
an  error  is  to  no  man's  credit.  It  was  my  good  fortune, 
however,  to  detect  this  error.  I  quickly  exposed  the  in- 
correctness of  my  1887  teaching  —  just  as  quickly  as  if 
another  had  been  the  unfortunate  one.  The  main  thought 
of  my  first  paper  was  that  oblique  astigmatism  was  more  an- 
noying than  the  vertical  or  horizontal,  because  in  the  former 
the  oblique  muscles  were  involved.  This  was  no  error.  I 
then  knew  nothing  of  the  obliquity  of  images  in  oblique 
astigmatism;  and,  believing  the  old  teaching  that  the  oblique 

*  Published  in  Annals  of  Ophthalmology  and  Otology,  July,  1S95. 

"(63) 


64  OBLIQUE   ASTIGMATISM. 

muscles  must  always  keep  the  naturally  vertical  meridians 
parallel,  I  readily  fell  into  the  error  of  teaching  that  the 
action  of  the  obliques  caused  by  oblique  astigmatism  was 
"harmonious  non-symmetric."  I  at  that  time  conceived  the 
purpose  of  the  rotation  to  be  to  bring  the  meridian  of  best 
curvature  to,  or  as  far  as  possible  toward,  the  vertical  or 
horizontal  position,  a  work  in  which  the  obliques  were  often 
aided  by  a  leaning  of  the  head  toward  the  shoulder.  I  then 
thought  that  vertical  (and  horizontal)  astigmatism  gave  least 
trouble,  because  of  the  mere  fact  of  position;  but  now  I  can 
understand  why  oblique  astigmatism,  with  meridians  of  great- 
est curvature  parallel,  will  give  as  little  trouble,  for  in  each 
of  these  conditions  any  object  will  throw  similar  images  on 
corresponding  retinal  parts.  For  the  reason  that  the  ob- 
liques do  not  have  to  perform  their  complicated  function 
in  these  forms  of  astigmatism,  their  correction  is  never 
attended  by  metamorphopsia  or  other  annoyance. 

I  try  always  to  "  have  a  reason  for  the  faith  that  is  within 
me,"  and  any  change  of  faith  or  teaching  on  my  part  must 
be  based  on  reason.  My  reason  for  abandoning  the  teach- 
ing of  harmonious  non-symmetric  action  of  the  obliques  in 
oblique  astigmatism,  and  in  its  place  teaching  that  these 
muscles  must  act  symmetrically,  is  that  the  refraction  of  such 
eyes  causes  the  formation  of  dissimilar  images  on  non-cor- 
'  responding  parts  of  the  retina?.  This  thought  of  oblique 
images  in   oblique   astigmatism   occurred  to  me   one  night 


REPLY  TO   DR.    HOTZ'S    CRITICISM. 


65 


early  in  1891,  and  the  next  day  I  was  able  to  demonstrate 
its  correctness,  not  only  to  my  own  satisfaction,  but  also  to 
the  complete  satisfaction  of  Dr.  G.  H.  Price.  I  did  not 
then  remember  that  Dr.  J.  A.  Lippincot  had  taught  us  this 
in  the  Archives  of  Ophthalmology,  March,  1889. 

Dr.  Hotz  complains  that  I  have  not  given  my  "method  of 
observation,"  and  that  I  failed  to  set  forth  "the  tests  or  ex- 
periments "  that  led   me  to  my  conclusions,  so  that  others 


RIGHT 


LEFT 


FIGURE    I. 


might  judge  for  themselves  as  to  the  correctness  of  the  same. 
This  accusation  was  certainly  inadvertent,  for  a  little  farther 
on  (page  105  of  your  last  issue)  he  quotes  my  experiment 
in  part.     I  give  it  here  in  full: 

"The  obliquity  of  the  image  in  oblique  astigmatism  is  a 
matter  demonstrable.  One  can  artificially  produce  any  kind 
of  astigmatism.  One  who  is  emmetropic,  or  at  least  is  non- 
astigmatic,  by  placing  a  — 3  D.  cylinder  before  each  eye  in 


66  OBLIQUE   ASTIGMATISM. 

trial  frames,  creates  3  dioptres  of  hypermetropic  astigmatism. 
The  axis  of  the  left  cylinder  being  at  900  and  that  of  the 
right  at  1350,  he  has  made  of  his  own  eyes  the  kind  repre- 
sented by  Fig.  2  [Fig.  1] .  He  may  now  for  a  moment  place 
the  opaque  disk  in  front  of  his  right  eye,  at  the  same  time 
placing  the  double  prism  (each  6°)  before  the  left  eye.  A 
horizontal  arrow,  head  to  left,  having  been  drawn  on  a  card- 
board, he  looks  through  the  double  prism,  and  sees  two  hor- 
izontal, hence  parallel,  arrows.  On  removing  the  opaque 
disk  from  the  right  side  of  the  trial  frame,  a  third  arrow  ap- 
pears between  the  other  two,  but  not  parallel  with  them — it 


FIGURE    2. 


is  oblique  down  and  to  the  patient's  left.  On  removing  the 
double  prism  two  arrows  are  at  once  readily  seen,  the  one 
crossing  the  other,  as  in  Fig.  8  [Fig.  2].  In  a  moment  the 
two  arrows  begin  to  shut  and  open  like  the  blades  of  a  pair  of 
scissors,  and  finally  they  are  merged  indefinitely  into  one." 
I  commenced  the  experiment  convinced  that  artificial 
astigmatism  would  produce  the  same  image  changes  which 
result  from  natural  astigmatism;  and  what  convinced  me 
was  that  my  3  D.  artificial  hypermetropic  astigmatism  was 
thoroughly  corrected  by  a  +  3  D.  cylinder,  axis  coinciding 
with  the  meridian  of  unaltered  curvature.  The  above  experi- 


REPLY   TO   DR.    HOTZ's    CRITICISM.  67 

merit  seems  to  be  convincing.  I  have  other  reasons  for  be- 
lieving in  the  obliquity  of  images,  and  will  give  some  of 
them  in  words  I  recently  used  in  the  "Journal: 

"  Let  Dr.  Hotz  take  any  case  of  astigmatism  of  more  than 
3D.,  with  the  meridians  of  greatest  curvature  either  vertical, 
horizontal,  or  oblique ;  and  if  the  patient  has  ordinary  intelli- 
gence, he  can  soon  satisfy  himself  that  astigmatism  is  not 
only  capable  of  blurring,  but  also  of  distorting  an  object. 
One  eye  should  be  excluded,  while  the  patient  is  asked  to 
look  at  a  rectangular  card  two  by  four  inches  held  verti- 
cally immediately  in  front  at  the  reading  distance.  As 
the  card  is  revolved  on  a  pin  piercing  its  center,  the 
patient  should  be  asked  its  shape  when  at  three  definite 
points.  When  the  long  sides  of  the 'card  are  parallel  with 
the  meridian  of  greatest  curvature,  the  patient  will  say 
that  it  is  a  rectangle;  when  these  sides  form  an  angle  of  450 
with  the  meridian  of  greatest  curvature,  the  answer  will  come 
quickly  that  it  is  a  parallelogram;  again,  when  these  sides 
are  brought  to  right  angles  with  the  meridian  of  greatest 
curvature,  the  card  again  is  seen  as  a  rectangle.  But  pos- 
sibly Dr.  Hotz  is  ready  to  say  that  these  statements,  as  to 
the  distortion  of  the  object,  prove  nothing  as  to  the  distor- 
tion of  the  retinal  image.  Let  us  see.  The  law  of  projec- 
tion (direction)  is  supreme  in  monocular  vision,  therefore 
the  lower  border  of  the  retinal  image  must  be  in  the  same 
plane  with  the  upper  border  of  the  card,  and  so  on  for  all 


68  OBLIQUE  ASTIGMATISM. 

the  borders  of  card  and  image;  and  these  planes  must  all 
cut  the  nodal  point.  Then,  in  obedience  to  this  law,  the  im- 
age must  be  distorted  when  the  object  appears  to  be. 

"  Only  one  other  argument  as  to  the  distortion  of  the  reti- 
nal image  in  an  astigmatic  eye,  when  the  object  is  held  so 
that  its  outlines  are  oblique  to  the  principal  meridians.  All 
will  agree  that  the  meridian  of  least  curvature  is  the  line  of 
union  of  the  bases  of  the  prismatic  arrangement  of  the  as- 
tigmatic cornea,  and  that  all  prisms  refract  light  toward  the 
base.  Let  us  then  take  the  right  eye  of  a  case  of  astigma- 
tism with  the  meridian  of  least  curvature  at  1350.  A  horizon- 
tal line  held  before  this  eye  will  send  its  light  from  its  entire 
length  into  the  eye,  but,  for  the  convenience  of  study,  we 
will  consider  only  the  axial  rays  coming  from  the  two  ex- 
tremities. The  ray  from  the  left  end  of  the  line  strikes  above 
the  meridian  of  least  curvature,  and  must  be  bent  toward 
it,  its  subsequent  course  in  the  eye  necessarily  being  down 
and  out ;  the  axial  ray  from  the  right  end  of  the  line  strikes 
below  the  meridian  of  least  curvature,  and  must  be  bent  to- 
ward it,  the  course  of  this  ray  after  refraction  being  up  and 
in.  Thus  it  is  easily  shown  that  the  image  of  this  horizon- 
tal line  must  be  inclined  down  and  to  the  right.  Because 
of  this  inclination  of  the  image  the  line  itself  seems  inclined 
to  the  same  extent,  and  in  the  same  direction.  This  is  one 
law  of  physiologic  optics. 

"The  distortion  of  retinal  images  in  monocular  vision  is 


REPLY  TO   DR.    HOTz's    CRITICISM.  69 

settled  by  the  law  of  direction;  the  rotation  of  the  eyes  by 
the  oblique  muscles,  in  oblique  astigmatism,  is  compelled  by 
the  more  powerful  law  of  corresponding  retinal  points." 

Dr.  Hotz  made  the  following  quotation  from  one  of  my 
papers:  "  In  oblique  astigmatism,  be  the  obliquity  much  or 
little,  it  is  a  physical  impossibility  for  the  horizontal  object 
and  its  retinal  image  to  occupy  the  same  plane.  The  same 
is  true  of  all  objects  not  in  a  plane  with  one  or  the  other  of 
the  two  principal  meridians."  Forgetting  that  the  closing 
sentence  of  the  above  quotation  had  been  made,  the  Doctor 
informs  me  and  your  other  readers  that  "  the  objects  in  na- 
ture are  not  all  horizontal  arrows,  but  present  also  vertical 
and  oblique  outlines,  .  .  .  unfortunately  for  Dr.  Savage's 
theory." 

The  fact  that  when  oblique  astigmatic  eyes  attempt  to  fuse 
images  of  a  horizontal  line,  the  images  of  a  vertical  line  har- 
monize less,  which  Dr.  Hotz  thinks  unfortunate  for  my  the- 
ory, is  favorable  to  my  teaching.  In  an  editorial  in  the 
Ophthalmic  Record,  referring  to  Dr.  Wilson's  criticism,  as 
published  in  the  Archives  of  Ophthalmology,  I  conceded 
that  the  same  eyes  could  fuse  images  of  either  horizontal  or 
vertical  lines  when  they  existed  alone;  for  example,  the  me- 
ridians of  greatest  curvature  diverging  above,  the  superior 
obliques  would  cause  the  fusion  of  the  images  of  a  horizon- 
tal line,  and  the  inferior  obliques  would  fuse  the  images  of 
a  vertical  line.     In  the  same  editorial  I  taught  that  when 


70  OBLIQUE   ASTIGMATISM. 

both  horizontal  and  vertical  lines  are  viewed  the  eyes  at- 
tempt the  fusion  of  the  horizontal  lines  only;  but  was  una- 
ble then,  and  am  unable  now,  to  give  any  reason  for  this. 
I  only  know  it  to  be  a  fact.  My  knowledge  of  the  fact  rests 
on  these  observations,  which  may  be  repeated  T?y  any  one: 
In  a  case  of  3  D.  astigmatism  with  meridian  of  greatest  cur- 
vature at  1 350  for  the  right  eye  and  450  for  the  left  eye,  if  a 
rectangle  be  looked  at  by  the  right  eye  alone,  it  will  be  seen 
as  a  parallelogram  leaning  down  and  to  the  left;  by  the  left 
eye  alone,  a  parallelogram  leaning  down  and  to  the  right; 
with  the  two  eyes  together,  it  will  be  seen  as  a  trapezoid  with 
the  longer  side  above.  By  action  of  the  superior  obliques  the 
upper  borders  of  images  (lower  border  of  object)  are  com- 
pletely fused,  while  at  the  same  moment  all  of  the  lower  bor- 
der of  right  image,  except  its  inner  extremity,  is  fused  with 
a  corresponding  portion  of  the  same  border  of  the  left  image. 
The  parts  of  the  lower  borders  of  the  two  images  not  fused 
are  directly  continuous  with  the  fused  portion,  hence  the 
greater  length  of  the  upper  border  of  the  object.  Of  the 
two  diverging  borders,  the  right  one  is  seen  by  the  right 
eye,  and  the  left  one  by  the  left  eye. 

If  the  meridians  of  greatest  curvature  had  converged 
above,  the  action  of  the  inferior  obliques  in  binocular  vision 
would  have  converted  the  rectangle  into  a  trapezoid  with  the 
longer  side  below.  As  already  stated,  this  preference  for 
fusing  horizontal  lines  is  distinctly  shown  in  the  higher  de- 


REPLY   TO   DR.    HOTZ  S    CRITICISM.  71 

grees  (3  D.  or  more)  of  natural  oblique  astigmatism.  It  is 
also  distinctly  shown  in  similar  degrees  of  artificial  astig- 
matism. The  chief  purpose  of  the  existence  of  the  recti 
and  the  oblique  muscles  is  the  fusion  of  images  in  binocular 
vision. 

As  to  Dr.  Hotz's  experiment  with  his  -f-10  3  Jr2  cylinder,  I 
have  this  to  say:  His  slit  in  the  metal  screen  was  entirely  too 
short  (one  inch)  to  be  so  far  removed  (several  feet)  from  the 
surface  representing  the  cornea.  Necessarily  this  slit  at 
such  a  distance  would  throw  a  very  small  image  on  the 
ground  glass  four  inches  behind  the  lens,  and  thus  make  it 
very  difficult  to  detect  the  slight  leaning  (less  than  20)  of 
the  borders,  caused  by  the  weak  cylinder  used.  A  slit  sev- 
eral inches  long  and  only  a  few  feet  away  from  the  lens, 
would  have  thrown  a  much  longer  image  on  the  ground  glass, 
so  that  the  very  slight  change  in  the  direction  of  the  image 
borders  could  have  been  easily  detected. 

Finally,  allow  me  to  try  to  break  in  pieces  the  keystone 
of  his  argumental  arch — viz.,  the  clinical  test  to  which  he 
put  my  theory.  The  case  reported  was  one  of  mixed  astig- 
matism, and  the  cylinder  given  the  right  eye  was  probably 
a  — 3  D.,  and  that  for  the  left  eye  a  — 2  D.  The  meridian 
of  greatest  curvature  in  O.  D.  was  at  115°;  in  O.  S.,  at65°. 
(These  meridians  diverged  above.  The  image  of  a  rectangle 
would  have  been  distorted  down  and  in  by  each  eye,  and  in  bi- 
nocular vision  these  leaning  parallelogram  images  would  have 


72  OBLIQUE   ASTIGMATISM. 

been  fused,  so  that  the  patient  would  have  seen  a  trapezoid, 
long  side  above.)  The  correcting  cylinders  were  given, 
and  metamorphopsia  was  observed  at  once  by  the  patient; 
but  he  does  not  give  the  character  of  the  changed  vision. 
Without  the  correcting  lenses  on,  he  resorted  to  a  test — the 
double  prism — which  he  states  that  I  had  advised,  and  he 
found  all  three  lines  parallel. 

My  first  stroke  at  this  "keystone"  will  be  with  the  state- 
ment that  I  have  never  resorted  to  this  test  by  the  double 
prisms  in  uncorrected  natural  oblique  astigmatism,  nor  have 
I  ever  advised  it.  I  would  expect  the  lines  to  be  parallel, 
for  the  obliques  from  habit  would  so  rotate  the  two  eyes  as 
to  make  the  lines  parallel.  If  he  had  used  the  double  prism 
test  on  his  patient,  while  wearing  her  spectacles  and  still 
troubled  with  the  metamorphopsia,  he  would  have  found 
want  of  parallelism  of  the  middle  lines  with  the  two  other 
lines — it  would  have  inclined  down  and  toward  the  corre- 
sponding side.  The  same  test  applied  after  the  disappear- 
ance of  the  metamorphopsia,  the  spectacles  being  on,  would 
show  parallelism  of  the  lines ;  but  removing  the  lenses  at  this 
time,  the  test  would  show  the  middle  line  leaning  down  and 
toward  the  opposite  side.  The  explanation  of  all  this  is 
easy : 

The  double  prism  test  in  oblique  artificial  astigmatism 
(this  I  did  advise)  will  always  show  the  dipping  of  the  mid- 
dle line,  because  the  habit  of  rotation  by  the  obliques  has 


REPLY   TO   DR.    HOTZS    CRITICISM.  73 

not  been  established.  In  Dr.  Hotz's  case  of  mixed  ob- 
lique astigmatism  the  superior  obliques  had  been  always  in 
the  habit  of  rotating  the  eyes,  and  this  habit  reasserted  it- 
self when  the  eyes  were  under  the  double  prism  test,  as  may 
always  be  expected,  and  the  lines  were  parallel.  If  the 
metamorphopsia  has  disappeared  under  the  wearing  of  the 
lenses,  the  double  prism  test  applied  to  the  naked  eyes  will 
show  the  middle  line  dipping  down  and  toward  the  opposite 
side,  for  the  habit  of  rotation  has  been  broken.  There 
never  was,  there  never  will  be,  a  time  in  this  case  when, 
with  the  naked  eyes,  there  was  not  metamorphopsia  of  that 
kind  which  would  have  made  a  rectangle  appear  as  a  trape- 
zoid, the  longer  side  above.  To  this  form  of  metamorphop- 
sia the  patient  had  always  been  accustomed,  and  therefore 
was  not  worried  about  it.  The  form  of  metamorphopsia 
with  the  lenses,  when  they  were  first  given,  was  a  new  kind 
— the  trapezoid  had  its  long  side  below,  necessarily — though 
the  Doctor  did  not  tell  so  much.  Being  new  to  the  patient, 
it  was  naturally  annoying.  An  explanation  of  this  new 
metamorphopsia  is  easy:  While  carrying  the  patient  through 
the  examination  for  the  lenses,  he,  of  course,  excluded  one 
eye.  The  uncovered  eye  naturally  rolled  into  the  position 
of  rest  of  all  the  ocular  muscles,  and  the  axis  of  the  cylinder 
for  that  eye  was  located.  Similarly  the  cylinder  was  given 
the  other  eye.  In  binocular  vision  the  old  habit  of  rotation 
by  the  superior  obliques  was  reasserted,  and  there  was  a  con- 


74  OBLIQUE   ASTIGMATISM. 

sequent  loss  of  coincidence  of  the  axes  of  the  cylinders  and 
the  meridians  of  least  curvature  (the  cylinders  were  con- 
cave), the  cylinder  axes  being  thrown  about  30  in  the  arcs 
of  distortion  for  the  inferior  obliques.  In  this  case  the 
metamorphopsia  could  disappear  only  by  the  superior  ob- 
liques giving  up  work  which  the  inferiors  must  take  on. 
Without  the  lenses  the  superior  obliques  have  been  forced 
to  converge  the  naturally  vertical  meridians ;  with  the  lenses 
on  the  inferior  obliques  must  parallel  these  meridians. 
Usually  this  change  is  quickly  accomplished  in  cases  like 
this  one.  Dr.  Hotz  will  not  deny  that  the  cvlinders  given 
changed  the  direction  of  the  images  of  vertical  and  horizon- 
tal lines.  To  my  mind  it  is  clear  that  the  leaning  of  images, 
caused  by  the  lenses,  was  equal  in  extent,  but  opposite  in 
direction,  to  that  produced  by  the  astigmatic  cornea.  The 
lenses  have  only  rectangled  the  images  of  the  rectangular 
figure.  If  in  these  cases  the  oblique  muscles  would  only 
allow  the  cylinder  axes  and  the  meridians  of  best  curva- 
ture to  remain  coincident  in  binocular  vision,  there  would  be 
no  such  thing  as  metamorphopsia  ever  complained  of.  It 
is  never  observed  by  patients  having  astigmatism  equal  in 
the  two  eyes  and  the  best  meridians  parallel,  though  they 
may  be  oblique.  When  the  meridians  of  greatest  curvature 
converge  above  the  use  of  correcting  cylinders  is  always  at- 
tended by  metamorphopsia,  which  is  slower  to  disappear 
than  in  cases  like  Dr.  Hotz's. 


REPLY   TO   DR.    HOTZ's    CRITICISM.  75 

Dr.  Hotz's  closing  paragraph,  if  true,  would  wipe  out  all 
that  I  have  ever  written  about  oblique  astigmatism  and  the 
oblique  muscles.  This  is  his  language:  "It  is  therefore 
evident  that  neither  experiments  nor  clinical  observations 
nor  the  laws  of  physiological  optics  sustain  the  doctrine  of 
the  obliquity  of  the  retinal  images  and  the  necessity  of  any 
action  of  the  oblique  muscles  in  oblique  astigmatism." 

In  another  part  of  this  reply  I  have  shown  conclusively 
that  both  experiment  and  clinical  observation  showed  my 
teaching  to  be  correct,  so  that  two  of  his  three  witnesses 
against  my  views  have  been  made  to  testify  for  them.  It 
is  even  easier  to  capture  his  third  witness  (physiological  op- 
tics), and  thus  make  the  trio  give  evidence  the  very  oppo- 
site to  that  which  he  intended  they  should  give.  Without 
doing  violence  to  the  laws  of  physiological  optics,  I  may 
state  that  every  point  of  an  astigmatic  cornea  has  two  radii 
of  curvature:  one  the  radius  of  spherical  curvature,  the 
other  the  radius  of  cylindrical  curvature.*  In  the  horizon- 
tal meridian  of  a  vertical  astigmatism  these  two  sets  of  radii 
are  in  the  same  plane,  hence  the  rays  of  light  entering  this 
eye  in  the  horizontal  meridian  would  be  in  the  same  plane 
after  refraction  as  before.  Above  or  below  the  horizontal 
meridian,  and  out  or  in  from  the  vertical  meridian,  there  is 

*  There  is  but  one  radius,  the  resultant  of  the  other  two.  This  radius 
is  not  that  of  a  spherical  or  a  cylindrical  surface,  but  of  a  sphero-toric 
surface. 


76  OBLIQUE   ASTIGMATISM. 

not  a  corneal  point  that  would  give  us  these  two  radii  in  the 
same  plane;  the  radius  of  spherical  curvature  would  go  to 
the  center  of  the  sphere,  while  the  radius  of  cylindrical 
curvature  would  necessarily  be  in  a  horizontal  plane.  Both 
of  these  radii  will  be  directed  to  the  plane  of  the  vertical 
meridian,  but  they  diverge  as  they  go.  A  ray  of  light 
striking  such  a  point  must  undergo  a  double  refraction  (a 
resultant  refraction).  If  the  corneal  point  is  thus  related  to 
the  horizontal  and  vertical  meridians,  the  ray  of  light  pass- 
ing through  it  must  be  deflected  toward  each  of  the  two 
radii;  therefore,  the  refracted  ray  can  no  longer  occupy  any 
plane  in  common  with  the  incident  ray. 

Allowing  the  retina  to  remain  in  its  normal  position,  let  us 
revolve  the  astigmatic  cornea  discussed  above,  so  that  the 
astigmatism  shall  be  oblique  at  an  angle  of  45°.  In  doing 
this,  we  have  not  altered  the  relationship  of  the  two  sets  of 
radii.  Those  that  were  in  the  same  plane  before  are  so  now: 
those  that  diverged  before  diverge  still.  Let  us  conceive  it 
to  be  the  right  cornea  and  that  the  meridian  of  least  curva- 
ture now  stands  at  450.  The  meridian  that  was  at  450  when 
the  astigmatism  was  vertical  stands  at  1800  when  the  astig- 
matism is  oblique  at  450.  What  happens  now  to  an  axial 
ray  in  the  horizontal  plane  ?  We  will  take  three  of  these 
rays  and  follow  them  as  they  make  their  way  to  the  retina. 
One  ray  is  from  the  middle  of  a  horizontal  line  (arrow,  if 
you  please),  one  is  from  one  end  of  the  line,  and  the  other 


REPLY  TO    DR.    HOTZ's   CRITICISM.  77 

is  from  the  other  end.  These  rays  must  converge  toward 
that  part  of  the  cornea  in  front  of  the  pupillary  space.  They 
come  to  the  eye  in  the  same  plane  and  strike  the  horizontal 
meridian  of  the  cornea.  The  point  of  fixation  is  the  center 
of  the  line ;  therefore  the  middle  of  these  three  rays  strikes 
the  center  of  the  cornea  vertically,  and  coincides  with  both 
the  radius  of  spherical  and  the  radius  of  cylindrical  curvature 
for  that  point,  hence  passes  through  the  cornea  without  be- 
ing refracted  at  all,  and  impinges  on  the  retina's  horizontal 
meridian.  The  ray  from  the  right  end  of  the  line  strikes 
the  right  side  of  the  cornea  at  a  point  in  the  horizontal  me- 
ridian, the  two  radii  of  which  diverge,  the  radius  of  spher- 
ical curvature  being  in  the  horizontal  plane,  the  radius  of 
cylindrical  curvature  pointing  down,  as  well  as  toward  the 
plane  of  the  meridians  of  least  curvature.  It  is  clear  that 
this  ray  must  undergo  a  double  (resultant)  refraction. 
Striking  the  cornea  to  the  temporal  side  of  the  radius  of 
spherical  curvature,  it  is  so  refracted  as  to  converge  less 
toward  the  middle  axial  ray  (in  this  it  is  aided  by  the  cylin- 
drical curvature),  and  being  incident  to  the  radius  of  cylin- 
drical curvature  on  its  lower  side,  it  must  be  refracted 
down  also.  Following  its  subsequent  course,  we  find  it  im- 
pinging on  the  retina  below  the  horizontal  meridian,  to  the 
nasal  side  of  the  vertical  meridian.  The  ray  from  the  left 
end  of  the  line,  coming  to  the  cornea  in  a  plane  with  the 
other  two,  strikes  the  cornea  on  the  nasal  side  of  its  center  and 


78  OBLIQUE   ASTIGMATISM. 

in  the  horizontal  meridian,  at  a  point  where  the  two  radii  di- 
verge, the  radius  of  spherical  curvature  being  in  the  hori- 
zontal plane  and  the  radius  of  cylindrical  curvature  pointing 
up  and  toward  the  plane  of  the  meridian  of  least  curvature. 
Striking  the  cornea  on  the  nasal  side  of  the  radius  of  the 
sphere,  this  ray  is  made  to  converge  less  toward  the  middle 
ray  than  before  refraction ;  striking  the  cornea  on  the  upper 
side  of  the  radius  of  cylindrical  curvature,  it  is  also  refracted 
upward.  Following  this  ray  to  the  retina,  we  find  it  im- 
pinging above  the  horizontal  and  on  the  temporal  side  of  the 
vertical  meridian.  A  line  drawn  through  these  three  points 
of  impingement  will  locate  the  image  of  the  line  (arrow) 
looked  at.  It  is  inclined  in  obedience  to  the  plain  law  of 
refraction  that  a  ray  of  light  in  passing  from  a  rarer  into  a 
denser  medium  must  be  refracted  toward  the  perpendicu- 
lar at  the  point  of  impingement. 

There  is  one  other  objection  which  Dr.  Hotz  brought  for- 
ward— viz.,  while  a  concave  cylinder  held  obliquely  in  front 
of  an  eye  at  some  distance  will  make  horizontal  and  vertical 
lines  appear  inclined  toward  its  axis,  this  inclination  grows 
less  and  less  as  the  eye  is  approached,  and,  as  he  thinks, 
disappears  entirely  when  the  cylinder  is  brought  into  con- 
tact with  the  cornea. 

This  is  all  easily  explained.  Take  again  the  three 
axial  rays  in  a  horizontal  plane.  Striking  the  horizontal 
portion  of  the  oblique  cylinder,  the  middle  ray  passes  through 


REPLY   TO   DR.    HOTZ'S    CRITICISM.  79 

unrefracred  and  continues  in  the  same  plane,  while  one  of 
the  outer  rays  is  made  to  deviate  downward,  and  the  other 
upward.     For  convenience  of   study  we  will  say    that    the 
deviation  of  each  ray  is  2°  from  the  horizontal  plane.     This 
deviation  continues  the  same  until  the  retina  is  reached,  re- 
gardless of  whether  this  distance  is  one  meter  or  25  mm.    In 
obedience  to  the  law  of  direction,  the  horizontal  line  is  made 
to   appear  to   incline  more   when  the  cylinder  is  held  one 
meter  from  the  eye  than  when  it  is  held  50  cm.  away.     In 
obedience  to  the  same  law,  the  line  appears  less  and  less  in- 
clined   as    the    oblique   cylinder  is   made  to   approach    still 
nearer  the  eye,  but    even  when    brought  into  contact  with 
the  spherical  cornea,  its  inclination  does  not  and  cannot  dis- 
appear entirely,  though  often  one  may  not  be  able  to  per- 
ceive that  there  is  still  an  inclination.    This  apparent  change 
in  the  direction  of  a  line,  viewed  through  a  concave  cylinder 
held  obliquely  as  it  is  moved  from  arm's  length  to  the  eye, 
could  not  be  explained  if  Helmholtz's  law  of  direction  were 
true.     If  the  axial  ray  were  the  line  of  direction,  the  appar- 
ent obliquity  of  a  horizontal  line  would  be  the  same,  whether 
the  cylinder  causing  the    phenomenon    were  held  at  arm's 
length  or  in  contact  with  the  eye,  for  the  reason  that,  after 
the  axial  rays  are  deflected,  some  above  and  some  below  the 
horizontal  plane,  they  pursue  a  straight  course  (except  for 
spherical  refraction)  to  the  retina,  whether  it  be  far  away  or 
near  by.     These  rays  prolonged,  according  to  Helmholtz, 


80  OBLIQUE   ASTIGMATISM. 

would  locate  the  source  of  the  light,  and  necessarily  would 
give  it  the  same  apparent  inclination  for  all  distances  at 
which  the  cylindrical  surface  might  be  held  from  the  eye. 
Not  so  with  that  law  of  direction  which  says  that  all  lines  of 
direction  are  radii  of  retinal  curvature  prolonged.  This  law 
makes  it  necessary  for  the  line  to  appear  to  incline  more 
when  the  cylinder  is  held  far  away  from,  and  less  when  it  is 
brought  close  to,  the  eye. 


CHAPTER  IV. 

OBLIQUITY  OF   RETINAL   IMAGES   IN  OBLIQUE 
ASTIGMATISM  AS  SHOWN  BY  PHOTOGRAPHY. 

Since  the  first  edition  of  this  book  was  brought  out,  pho- 
tography has  been  called  in  to  give  evidence  as  to  the  teach- 
ings found  in  Chapters  I.  and  II.  of  that  edition  (I.  and  V. 
of  this  edition).  Dr.  Harold  Wilson  asked  the  camera  to 
prove  that  the  teachings  were  false,  by  showing  that  an  as- 
tigmatic lens  did  not  distort  images  on  the  sensitive  plate. 
He  took  several  photographs  of  a  church  spire :  one  with  a 
nonastigmatic  lens;  one  with  an  astigmatic  lens,  axis  at  900; 
two  with  axis  at  45 °  ;  and  two  with  axis  at  1350.  From  these 
several  photographs  half-tone  cuts  were  made,  which  were 
used  by  him  to  illustrate  his  paper,  which  was  published  in 
the  "Journal  of  Ophthalmology ,  Otology,  and  Laryngology , 
July,  1895.  He  claimed  that  these  photographs  showed  con- 
clusively that  an  astigmatic  cornea  does  not  distort  retinal 
images;  and  therefore,  the  teaching  that,  in  oblique  astig- 
matism, the  oblique  muscles  must  act  harmoniously  and  sym- 
metrically had  no  foundation  in  fact.  Sometimes  in  court 
a  witness,  called  to  give  evidence  favoring  one  side,  states 
facts  that  are  clearly  in  favor  of  the  other  side  of  the  case. 
So  it  was  with  Dr.  Wilson's  camera:  the  cause  that  he  wished 
6  (81) 


82  IMAGES   IN   OBLIQUE   ASTIGMATISM 

to  hurt  he  helped.  In  his  first  two  photographs  the  axis  of 
the  spire  and  the  cornice  at  the  base  were  at  right  angles, 
the  only  difference  between  them  being  in  distinctness  of 
outline.  He  expected  the  reader  to  believe  with  him  that 
the  same  was  true  of  the  remaining  pictures.  These  speak 
for  themselves,  each  one  saying  that  the  axis  of  its  spire  is 
not  at  right  angles  with  the  cornice  at  its  base.  In  each, 
these  lines  had  been  distorted  from  the  axis  of  the  cylindric- 
al lens  (toward  the  meridian  of  greatest  curvature).  This  is 
just  what  we  had  shown  before,  independent  of  the  aid  of  the 
camera.  It  would  be  interesting  to  reproduce  Dr.  Wilson's 
cuts,  but  we  did  not  think  in  time  to  ask  him  for  the  privi- 
lege of  using  them.  We  will  present,  however,  half-tone 
cuts  showing  exactly  what  his  pictures  distinctly  set  forth. 
These  cuts  were  made  from  photographs  of  a  rectangle 
taken  by  Dr.  Lowry,  at  our  suggestion,  and  under  the  con- 
ditions observed  by  Dr.  Wilson.  We  reproduce  not  only 
the  cuts,  but  also  the  words  used  by  Dr.  Lowry  in  a  short 
paper  published  in  the  Ophthalmic  Record,  August,  1895 : 

"  It  has  often  been  noted  that  the  camera  obscura  is  very 
strikingly  similar,  in  its  mechanism,  to  the  human  eye.  In 
this  simple  optical  instrument  we  have  a  mechanical  eye,  so 
far  as  refraction  is  concerned.  If  we  compare  to  the  eye 
the  component  parts  of  the  photographic  camera,  which  is 
merely  a  camera  obscura  with  a  device  for  receiving  the  im- 
age on  a  sensitized  plate,  we  find  the  refractive  media  of  the 


AS   SHOWN   BY   PHOTOGRAPHY.  83 

former  correspond  to  the  photographic  lens;  the  iris,  to  the 
stop;  the  accommodation,  to  the  focusing  apparatus;  and 
the  retina,  to  the  ground  glass.  Focus  the  camera  properly, 
and  we  have  the  emmetropic  eye.  By  placing  a  concave 
cylindrical  lens,  axis  at  900,  in  apposition  to  the  photo- 
graphic lens,  we  have  simple  hypermetropic  astigmatism  ac- 
cording to  the  rule.  If  we  place  the  axis  at  1800,  we  have 
simple  hypermetropic  astigmatism  against  the  rule.  If  we 
place  the  axis  anywhere  between  the  vertical  and  horizontal, 
we  get  oblique  astigmatism.  Whether  or  not  the  image  will 
be  oblique  on  the  ground  glass  will  be  seen  later. 

"  To  illustrate  these  points,  I  have  made  the  accompany- 
ing photographs  with  a  rapid  rectilinear  lens,  used  in  the 
the  Rochester  Optical  Company's  5x7  midget  camera.  The 
camera  was  not  moved  or  changed  in  any  way  for  the  first 
five  photographs.  Fig.  6  was  made  at  another  time.  The 
rectangle  was  made  mathematically  accurate  on  a  piece  of 
cardboard  24x30.  The  lines  one  inch  wide  are  prolonged 
beyond  the  rectangle  to  show  more  clearly  the  obliquity  that 
may  be  produced  by  the  cylinders,  obliquely  placed.  The 
watch  is  used  as  a  plumb,  and  is  seen  in  the  same  position 
in  all.  The  photographs  are  not  inverted  as  the  images 
would  be  on  the  ground  glass  or  the  retina. 

"  In  Fig.  1,  no  cylindrical  lens  is  used,  and  we  get  a  per- 
fect rectangle,  sharp  and  distinct  in  its  outline,  as  would  be 
seen  by  an  emmetropic  eye. 


TC  IB 

Kff  S 

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Bat  JO 

i — -BL ! _ —  ^^  


FIGURE    I. 


(S4) 


FIGURE    3. 


FIGURE   4. 


(85) 


86  IMAGES   IN   OBLIQUE   ASTIGMATISM. 

"  In  making  Fig.  2,  a  — 3  D.  cylindrical  lens  is  placed  just 
in  front  of,  and  in  apposition  to,  the  photographic  lens,  with  its 
axis  at  450.  A  +1.50  D.  spherical  lens  is  used  with  the 
cylinder  in  order  to  give  the  middle  of  the  focal  interval 
without  changing  the  camera.  In  this  the  vertical  and  hori- 
zontal lines  are  equally  indistinct.  The  vertical  lines  deviate 
to  the  left  at  the  top,  and  to  the  right  at  the  bottom,  while 
the  horizontal  lines  are  depressed  at  the  right  and  elevated 
at  the  left.  The  plumb  shows  that  the  card  is  in  just  the 
same  position  as  in  Fig.  1,  and  the  camera  has  not  been 
moved  from  its  original  position.  This  picture  is  clearly  a 
nonrectangular  parallelogram. 

"  If  the  axis  of  the  cylinder  be  changed  to  90°,  we  get 
Fig.  3,  which  represents  simple  vertical  hypermetropic  as- 
tigmatism. This  is  made  without  the  +1.50  D.  sphere,  and 
without  the  camera  being  changed  in  the  least  from  its  po- 
sition in  Figs.  1  and  2.  The  meridian  of  greatest  curvature 
here  is  at  900,  with  the  least  at  180°.  It  is  a  perfect  rec- 
tangle with  its  horizontal  lines  sharply  cut  and  the  vertical 
very  indistinct. 

"  Now  if  we  place  the  axis  of  the  cylinder  at  1350,  again 
adding  the  +1.50  D.  sphere,  a  nonrectangular  parallelogram 
is  formed  with  its  sides  deviating  in  the  opposite  direction  to 
those  in  Fig.  2.  This  is  shown  in  Fig.  4.  Every  part  is 
equally  indistinct,  and  nowhere  are  the  lines  at  right  angles 
as  in  the  original. 


• 

i 

» 

I 

>. 

,___ . ___  ■■•BLi,,*. 

•  -  a 

■< 

I 

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FIGURE    5. 


FIGURE    6 


88  IMAGES   IN   OBLIQUE   ASTIGMATISM 

"  By  placing  the  axis  of  the  cylinder  at  i8oQ,  without  the 
-{-1.50  D.  sphere,  we  produce  simple  hypermetropic  hori- 
zontal astigmatism,  the  effect  of  which  is  illustrated  in  Fig. 
5.  Here  we  have  the  meridian  of  greatest  curvature  at 
1800,  and  the  least  at  900.  We  obtain  a  perfect  rectangle, 
with  its  vertical  lines  clear  and  its  horizontal  very  indistinct, 
in  contradistinction  to  Fig.  3. 

"Fig.  6  is  the  same  as  Fig.  2  without  the  +1.50  D.  sphere 
to  give  the  focal  interval,  nor  is  the  camera  refocused  to  give 
it.  This  photograph  was  made  at  a  different  time,  and  the 
camera  was  not  in  exactly  the  same  position  as  for  the  other 
five.  An  eye  with  the  meridian  of  greatest  curvature  at  450 
and  3  D.  of  simple  hypermetropic  astigmatism,  would  see  the 
object  as  shown  in  this  figure,  if,  under  the  influence  of  a 
mydriatic,  or  in  old  age,  it  was  relieved  of  all  ciliary  action. 
The  rhomboidal  figures  are  seen  very  clearly  here  at  the  an- 
gles and  on  the  watch. 

"  It  is  very  evident  that  if  we  had  3  D.  of  hypermetropic 
astigmatism  in  each  eye,  with  their  meridians  of  greatest 
curvature  parallel  at  450,  each  eye  would  see  the  object  as 
seen  in  Fig.  2 ;  for  the  rays  of  light  from  each  point  of  the 
object  would  strike  corresponding  points  of  each  retina,  and 
the  two  images  would  be  superimposed,  giving,  in  binocular 
vision,  but  one  image,  distorted  as  shown  in  Fig.  2.  The 
person,  always  having  been  accustomed  to  seeing  vertical  and 
horizontal  objects  deviating  from  their  normal  position,  would 


AS    SHOWN   BY   PHOTOGRAPHY.  89 

suffer  no  inconvenience  from  the  error  other  than  ciliary 
strain  brought  about  by  an  attempt  to  place  the  image  at  the 
middle  of  the  focal  interval  in  order  to  get  the  most  distinct 
image  of  all  its  parts. 

"  Many  of  the  headaches  and  so-called  neuralgias  that  are 
complained  of  by  school  children,  young  and  middle-aged 
people,  who  use  their  eyes  for  close  work  (such  as  reading, 
sewing,  etc.)  are  due  to  this  strain,  andean  be  corrected  by 
placing  before  their  eyes  the  proper  cylinders  with  their  axes 
at  the  proper  angle,  which  will  at  the  same  time  correct  the 
obliquity  of  the  image.  As  mentioned  previously,  in  old  age, 
when  there  is  want  of  accommodation,  or  under  the  influ- 
ence of  a  mydriatic,  this  strain  is  relieved,  but  the  image  is 
not  made  more  distinct.  That  oblique  astigmatics  do  really 
see  objects  distorted  is  proved  by  the  fact  that  some  of  the 
noted  painters,  suffering  from  uncorrected  astigmatism,  in 
placing  on  canvas  what  should  be  vertical,  so  far  deviated 
from  that  direction  as  to  mar  their  otherwise  fine  paintings. 

"  The  same  ciliary  strain  is  noticed  in  vertical  and  horizon- 
tal asthmatics,  and  for  the  same  reason.  It  should  be  stated, 
however,  that  there  is  no  ciliary  strain  in  myopic  astigma- 
tism for  distance,  as  any  effort  on  the  part  of  this  muscle 
would  tend  to  make  vision  worse  instead  of  better,  and  any 
strain  is  an  attempt  in  some  way  at  an  improvement  of  the 
image  of  an  object. 

"  Suppose  one  of  the  meridians  of  greatest  curvature  to  be 


90  IMAGES    IN   OBLIQUE   ASTIGMATISM 

at  450,  and  the  other  at  1350,  one  image  would  be  seen  as  in 
Fig.  2,  and  the  other  as  in  Fig.  4;  in  obedience  to  the  law 
of  corresponding  retinal  points,  we  would  have  these  two 
figures  superimposed,  forming  a  trapezoid.  If  the  merid- 
ians diverged  above,  we  would  have  the  long  side  above,  and 
the  short  side  below.  In  this  form  of  astigmatism  we  would 
not  only  have  a  ciliary  strain,  but  the  superior  obliques 
would  make  an  attempt  to  bring  the  harmonizing  parts  of 
the  two  retinas  under  the  dissimilar  images  in  order  to  have 
a  single  image.  If  the  meridians  converged  above,  the  short 
side  of  the  trapezoid  would  be  above,  and  the  long  side  be- 
low. This  fusion  of  dissimilar  parallelograms  into  a  trape- 
zoid, long  side  below,  would  be  effected  by  the  inferior  ob- 
liques. Dr.  Savage  has  shown  this  very  clearly  in  his  pa- 
per read  at  the  Edinburgh  Congress. 

"  But  the  bone  of  contention  has  been  principally  the 
question  of  the  deviation  or  the  nondeviation  of  the  image 
on  the  retina  in  oblique  astigmatism.  Others  have  proved 
it  by  the  laws  of  optics,  by  clinical  experience,  and  by  log- 
ical reasoning;  and  it  seems  to  me  that  my  photographic 
demonstrations  have  added  very  conclusive  evidence  to  Dr. 
Savage's  theory  that,  in  oblique  astigmatism,  the  retinal  im- 
ages of  vertical  and  horizontal  objects  deviate  from  their 
normal  direction." 

Not  knowing  that  either  Dr.  Wilson  or  Dr.  Lowry  were 
at  work  with  the  camera  (the  one  to  disprove,  the  other  to 


AS   SHOWN   BY   PHOTOGRAPHY.  91 

prove,  what  we  have  taught  on  the  subject  of  oblique  astig- 
matism and  the  oblique  muscles),  Dr.  Perry,  of  Oneida,  N. 
Y., undertook  some  experiments  with  his  camera  with  neither 
object  in  view,  but  wholly  for  another  purpose.  With  only 
one  aim  in  view  primarily,  he  accomplished  two  things 
finally.  The  unexpected  result  which  he  attained  was  the 
confirmation  by  photography  of  our  views  on  the  distortion 
of  retinal  images  by  oblique  astigmatism.  His  paper,  illus- 
trated by  his  photographs  of  Jaeger  print,  was  published  in 
the  Ophthalmic  Record,  August,  1895.  We  quote  from  this 
paper  the  following: 

"  When  photographs  7  and  8  [4  and  5  in  his  original  pub- 
lication] were  taken,  one  end  of  the  line  was  found  to  be 
higher  than  the  other,  showing  the  screwlike  direction  of 
the  rays  referred  to  by  Dr.  Harold  Wilson,  of  Detroit,  in  his 
article  in  the  Archives  of  Ophthalmology,  July,  1894. 

"When  the  two  cards  (one  representing  astigmatism  of 
450,  and  the  other  one  of  135°)  are  put  in  a  stereoscope  in 
such  a  way  that  one  card  is  seen  with  the  right  eye  and  the 
other  with  the  left,  it  is  found  that  one  end  of  each  must  be 
raised  from  one-eighth  to  one-fourth  of  an  inch  to  make  the 
two  images  blend.  After  the  blending,  the  ends  may  be 
carried  still  higher  or  dropped  back,  so  as  to  be  nearly  par- 
allel without  separating  the  images.  This  tends  to  confirm 
the  theory  of  Dr.  Savage  that  the  images  in  symmetrical  ob- 
lique astigmatism  are  blended  by  the  rolling  of  the  eyeballs 


Q2  IMAGES    IN   OBLIQUE   ASTIGMATISM 

on  their  antero-posterior  axes  by  the  action  of  the  oblique 
muscles.  The  two  cards  pivoted  to  a  third,  which  fits  an 
ordinary  stereoscope  and  arranged  to  move  synchronously, 
make  a  simple  and  inexpensive  apparatus  for  exercise  of  the 
oblique  muscles. 

"  The  fact  noted  by  Dr.  Wilson,  that  in  oblique  astigma- 


NO.  7. 

tism  the  projection  of  the  vertical  line  is  turned  in  a  direc- 
tion contrary  to  the  horizontal,  seems  not  to  be  a  practical 
objection  to  the  theory  of  Dr.  Savage,  as  in  reading  we  see 
only  horizontal  lines — that  is,  we  see  whole  words,  however 
long,  without  seeing  the  line  above  or  below." 

In  commenting  on  the  last  paragraph  above  quoted,  it  may 
be  said  that  Dr.  Wilson  was  not  the  first  to  point  out  that,  in 


AS   SHOWN   BY   PHOTOGRAPHY.  93 

oblique  astigmatism,  "  the  vertical  line  is  turned  in  a  direc- 
tion contrary  to  the  horizontal."  In  1891  we  taught  that  all 
lines  not  parallel  with,  or  at  right  angles  to,  the  meridian  of 
greatest  curvature  are  deflected  toward  it,  hence  the  vertical 
in  a  direction  contrary  to  the  horizontal. 

Still  pursuing  his  studies  of  the  distortion  of  the  retinal 


NO.   8. 

images  by  oblique  astigmatism,  Dr.  Perry  was  able  to  have 
another  ingenious  half-tone  cut  made,  which  he  used  to  illus- 
trate another  paper,  which  was  published  in  the  Ophthalmic 
Record,  November,  1895.  This  paper  is  so  full  of  both 
truth  and  interest  that  we  reproduce  it  here  in  full : 

"The  experiments  described  below  were  made  to  deter- 
mine whether  adjustment  for  binocular  vision,  in  symmetrical 


94  IMAGES    IN   OBLIQUE   ASTIGMATISM. 

oblique  astigmatism,  involves  a  movement  of  rotation  on  the 
visual  axes. 

"  It  is  intended  to  show  experimentally:  First,  that  an  as- 
tigmatic lens  or  dioptric  system  so  distorts  the  visual  im- 
age as  to  deflect  radial  lines  on  opposite  sides  of  its  axis  in 
contrary  directions;  secondly,  that  when  such  images  are 
formed  on  the  retina?  of  a  pair  of  symmetrically  oblique  as- 
tigmatic eyes,  rotation  takes  place  in  the  direction  required 
to  carry  corresponding  points  of  each  retina  to  correlative 
points  in  the  image. 

"Fig.  9  was  produced  by  taking  a  photograph  of  the 
graduated  circle  with  printed  words  as  shown;  and  then, 
without  moving  camera  or  object,  placing  a  .50  D.  cylindric- 
al lens  in  front  of  the  objective  and  exposing  a  second  neg- 
ative, and  when  the  photographs  were  finished,  cutting  away 
the  outer  circle  from  the  astigmatic  print  and  pasting  it  over 
the  other  in  such  a  way  as  to  make  the  horizontal  and  vertic- 
al lines  respectively  coincide  on  the  two  prints.  If  the  cut 
is  held  so  that  the  line  of  the  print  reading  "Astigmatism 
Oblique  1350  "  is  horizontal,  it  will  be  observed  that  the  dis- 
tortion of  the  field  is  such  that  this  particular  line  is  moved 
along  the  scale  nearly  two  degrees,  while  the  line  which  is 
perpendicular  to  it  is  moved  an  equal  distance,  but  in  a  con- 
trary direction.  This  shows  what  must  happen  to  a  retinal 
image  in  oblique  astigmatism. 

"  Fig.  to  represents  a  stereoscopic  card  to  which  are  cen- 


'    / 


ss 


/ 


\\  .Mi  id.    ! 


v^- 


FIGURE  9. 


(95) 


96 


IMAGES    IN   OBLIQUE   ASTIGMATISM 


trally  pivoted  two  thin  disks,  each  three  inches  in  diameter, 
their  centers  being  three  inches  apart  in  a  horizontal  line." 

"These  disks  are  mashed  together  at  their  point  of  con- 
tact by  a  single  interlocking  slot  in  each. 

"  The  left  disk  is  moved  by  a  lever  passing  under  the 
right,  and  is  provided  with  an  index,  which  shows  on  a 
graduated  scale  at  the  right-hand  of  the  card  the  number  of 
degrees  that  each  disk  is  rotated.  Having  equal  diameters, 
and  being  geared  together,  they  move  synchronously  equal 


FIGURE    IO. 


distances,  but  in  opposite  directions.  Horizontally  over  the 
center  of  each  disk  is  printed  a  word,  and  vertically  through 
each  of  said  centers  is  drawn  a  line. 

"  When  this  apparatus  is  seen  in  a  stereoscope  and  the 
disks  are  rotated  by  moving  the  lever,  the  two  words  will  re- 
main blended  while  each  disk  moves  through  an  arc  of  about 
5°   (and   much  more  in  some  subjects);  and  if  attention  is 


AS    SHOWN  BY   PHOTOGRAPHY.  97 

given  to  the  perpendicular  lines,  they  will  appear  as  a  single 
line  during  the  rotation  of  about  the  same  arc.  If  used  with 
due  care,  this  instrument  gives  a  practically  accurate  meas- 
urement not  only  of  the  relative,  but  of  the  absolute,  power 
of  rotation  in  each  direction. 

"To  make  the  concluding  part  of  the  experiment,  the  card 
must  be  immovably  secured  to  the  stereoscope,  which  should 
be  rigidly  fixed  to  a  table  or  stand  provided  with  a  chin  rest, 
and  while  the  subject  of  the  experiment  is  looking  at  the 
words,  an  assistant  should,  by  moving  the  lever,  rotate  the 
disk  about  50  back  and  forth — that  is,  carry  the  index  about 
2  *^°  above,  then  2)4°  below,  the  point  marked  o  on  the  scale. 
During  this  rotation,  if  the  operator  observes  the  ophthalmo- 
scopic erect  image  of  a  vessel  on  the  nasal  side  of  the  retina, 
he  will  see  it  move  downward  over  the  field  of  the  pupil  as 
the  upper  edges  of  the  disks  are  rotating  outward,  and  up- 
ward when  they  are  rotating  inward. 

"  If  the  subject  of  the  experiment  now  gives  his  attention 
to  the  vertical  lines,  the  vessel  is  seen  to  move  up  when  the 
disks  are  rotating  outward,  and  down  when  they  are  rota- 
ting inward — that  is,  in  a  direction  opposite  to  that  seen  when 
the  word  or  horizontal  line  is  observed.  If  a  conjunctival 
vessel  is  observed  with  a  microscope  under  the  same  con- 
ditions, no  decided  motion  can  be  seen. 

"  The  facts  demonstrated  by  the  first  of  the  above-de- 
scribed experiments  have  been  proved  in  a  variety  of  ways, 


98  IMAGES   IN    OBLIQUE   ASTIGMATISM 

the  result  of  the  demonstration  by  geometrical  optics  being 
unquestionable;  but,  so  far  as  the  writer  is  informed,  the  di- 
rect observation  of  the  rotary  movement  of  the  eyeball  under 
the  conditions  stated  is  not  on  record." 

At  first  our  critics  intrenched  themselves  behind  the  dec- 
laration that  an  astigmatic  cornea  is  incapable  of  distorting 
images  whose  outlines  are  not  parallel  with,  or  at  right  an- 
gles to,  the  meridian  of  greatest  curvature.  They  character- 
ized our  declaration  of  this  distortion  as  false.  They  rea- 
soned that  since  there  is  no  distortion  of  images  there  can 
be  no  need  for  the  harmonious  symmetric  action  of  the  ob- 
lique muscles.  If  they  were  correct  in  their  concept,  their 
deduction  would  necessarily  be  true.  We  were  willing  to 
meet  them  on  their  own  ill-chosen  ground,  and  either  fall 
in  the  contest  or  drive  them  from  the  nondistortion  fort 
which  they  had  erected.  The  result  of  the  contest  on  this 
question  we  leave  to  the  judgment  of  him  who  will  read 
carefully  the  first  four  chapters  of  this  book.  We  claim 
that  observation,  clinical  experience,  physiologic  optics  and 
photography  all  agree  in  establishing  the  doctrine  that  an 
astigmatic  cornea  distorts  the  images  of  all  objects  whose 
outlines  are  not  parallel  with,  or  at  right  angles  to,  the  merid- 
ian of  greatest  curvature.  If  these  images  are  distorted  in 
opposite  directions  in  the  two  eyes,  then  there  must  be  har- 
monious symmetric  action  of  the  oblique  muscles  in  order 
to   harmonize  the  images,    so   as    to    give    binocular   single 


AS    SHOWN    BY    PHOTOGRAPHY.  99 

vision.  To  believe  otherwise,  one  must  deny  that  the  su- 
preme law  of  binocular  single  vision  is  the  law  of  corre- 
sponding retinal  points. 

If  we  have  succeeded  in  establishing  the  fact  that  the  ob 
lique  muscles  are  called  into  special  action  when,  in  astig- 
matism, the  meridians  of  greatest  curvature  converge  or  di- 
verge above,  we  have  succeeded  at  the  same  time  in  con- 
firming the  correctness  of  our  method  of  exercising  weak 
oblique  muscles,  as  set  forth  in  Chapter  V.  If  what  is  taught 
in  the  first  four  chapters  of  this  book  is  true,  the  teaching  of 
Chapter  V.  cannot  be  false. 


CHAPTER  V. 

INSUFFICIENCIES   OF    THE    OBLIQUE    MUSCLES 
AND  HOW  TO  CORRECT  THEM.* 

In  the  Archives  of  Ophthalmology ,  Vol.  XX., No.  i,  1891, 
I  announced  my  discovery  of  "  Insufficiency  of  the  Oblique 
Muscles."  I  closed  that  paper  by  saying  of  the  nervous 
symptoms  brought  about  by  this  state:  "  I  can  see  no  hope 
of  prevention  or  cure."  On  the  17th  day  of  May,  1892, 
while  a  patient  was  before  me,  whom  I  had  known  to  be  a 
sufferer  from  this  condition  for  two  years,  and  to  whom  I 
had  often  said,  "  There  is  not  now,  nor  can  I  see  how  there 
ever  can  be,  any  relief  for  this  trouble,"  a  thought  of  the 
proper  means  of  correction  dawned  upon  me.  I  at  once  ap- 
plied, in  this  case,  the  newly  thought  of  principle,  and  with 
the  most  gratifying  results.  Of  this  case  I  shall  have  more 
to  say  before  closing  this  paper. 

Before  setting  forth  the  treatment  I  will  refer  to  the  con- 
dition itself,  and  the  proper  means  of  detecting  it.  In  doing 
this,  since  I  cannot  do  better,  I  quote  from  my  paper  pub- 
lished in  the  Archives: 

*  Read  before  the  Section  of  Ophthalmology  of  the   American  Medical 
Association,  at  Detroit,  June,  1892. 
(100) 


HOW    TO    CORRECT    THEM.  IOI 

"  Every  ophthalmic  surgeon,  however  skilled  in  cor- 
recting errors  of  refraction,  and  in  operating  for  the 
different  known  forms  of  heterophoria,  has  had  cases  of 
eye -strain  for  which  he  could  do  but  little.  In  in- 
vestigating a  few  such  cases  during  the  last  six  months,  I 
have  found  the  cause  to  be  a  want  of  equilibrium  on  the 
part  of  the  oblique  muscles.  The  detection  of  this  condition 
is  easy.  I  place  a  double  prism  (my  modification  of  the 
Maddox  prism)  before  one  eye,  the  other  for  the  moment 
being  covered,  and  ask  the  patient  to  look  at  a  horizontal 
line  on  a  card  held  eighteen  inches  away.  The  effect  of 
the  double  prism  (each  6°,  bases  in),  so  placed  that  the  axis 
is  vertical,  is  to  make  the  line  appear  to  be  two,  each  paral- 
lel with  the  other.     The  other  eye  is  now  uncovered,  and  a 

third  line  is  seen  between  the  other  two,  with  which  it  should 

be  perfectly  parallel. 

"  While  a  change  of  the  position  of  the  axis  of  the  double 

prism,  from  the  vertical  toward  the  horizontal,  will  alter  the 

distance  between  the  lines,  their  direction  will  be  unchanged ; 

hence  no  loss  of  parallelism.     This  fact  admits   of  a  little 

carelessness  in  the  placing  of  the  prism  in  the  trial  frames ; 

though  the  axis  should  be  vertical,  so  as  to  give  the  maximum 

distance  between  the  two  extreme  lines. 

"  If  there  is  a  want  of  harmony  on  the  part  of  the  oblique 

muscles,  this  test  will  show  it  at  once  in  a  want  of  parallelism 

of  the  middle  with  the  two  other  lines,  the  right  end  of  the 


I02  INSUFFICIENCIES   OF   THE   OBLIQUE   MUSCLES: 

middle  line  pointing  toward  the  bottom  and  the  left  end 
toward  the  top  line,  or  vice  versa,  depending  on  the  nature 
of  the  individual  case.  9    , 


TVg. 


Fig.  SL 

£.  g,  <i 


Fig.  4. 
«  £  J  ■ 


Fig.  5. 


"In  my  investigations,  I  have  always  considered  the  eye 
before  which  no  prism  is  held  as  the  one  under  test.  With 
the  double  prism  before  the  right  eye,  the  patient  is  asked 
about  the  position  and  the  direction  of  the  middle  line.  It 
may  be  nearer  the  bottom,  thus  showing  left  hyperphoria; 


HOW   TO   CORRECT   THEM.  IO3 

or  again,  it  may  extend  farther  to  the  right  than  the  other 
two  and  not  so  far  to  the  left,  thus  showing  exophoria ;  or 
vice  versa,  showing  esophoria. 

"  If  the  right  ends  of  the  middle  and  bottom  lines  con- 
verge while  the  left  ends  diverge,  the  superior  oblique  of 
the  left  eye  is  at  once  shown  to  be  in  a  state  of  underaction. 
Figure  i  represents  such  a  test  of  the  left  eye.  Figure  2 
shows  a  test  of  the  left  eye  when  the  inferior  oblique  is  the 
too  weak  muscle.  Figure  3  represents  a  test  of  the  right 
eye,  the  loss  of  the  parallelism  between  the  lines  being  due 
to  underaction  of  its  superior  oblique ;  and  Figure  4,  the 
same  condition  of  the  inferior  oblique  of  the  right  eye. 
Figure  5  represents  a  test  of  both  eyes  when  there  is  perfect 
equilibrium  of  the  oblique  muscles. 

"As  is  well  known,  the  function  of  the  oblique  muscles  is 
to  keep  the  naturally  vertical  meridians  of  the  two  corneas 
parallel  even  when  not  vertical  [except  in  cases  of  uncor- 
rected oblique  astigmatism,  as  shown  in  Vol.  1,  No.  I,  of 
the  Ophthalmic  Record~\.  This  must  be,  or  a  troublesome 
form  of  double  vision  will  result.  If  there  is  perfect  equi- 
librium of  the  obliques,  this  parallelism  of  the  meridians 
named  is  maintained  without  trouble;  but  if  the  superior  ob- 
lique of  either  eye  be  too  strong  for  its  inferior,  or  vice  versa, 
the  parallelism  of  the  vertical  meridians  is  preserved,  and 
double  vision  is  prevented,  only  by  excessive  work  on  the 
part  of  the  weaker  muscles.     This  condition  of  the  oblique 


104  INSUFFICIENCIES   OF   THE   OBLIQUE   MUSCLES: 

muscles  brings  on,  at  longer  or  shorter  intervals,  a  train  of 
nervous  symptoms  for  which,  at  present,  I  can  see  no  hope 
of  prevention  or  cure." 

As  can  be  readily  seen,  the  condition  described  in  the  Ar- 
chives was  symmetrical  insufficiency  of  the  obliques.  Up  to 
that  time  I  had  not  seen,  nor  had  I  heard  of,  a  case  of  non- 
symmetrical insufficiency  of  the  obliques. 

Dr.  Moulton,  however,  reported  such  a  case  in  a  letter* 
to  the  editor  of  the  Ophthalmic  Record.  I  had  reasoned 
that  such  a  condition  would  not  give  trouble,  since  the 
strong  muscles  would  be  allowed  to  overact,  thus  revolving 
the  two  eyes  in  the  same  direction,  but  causing  no  disturb- 
ance of  vision.  I  still  believe  this  reasoning  correct  except 
in  cases  of  corrected  astigmatism.  Such  a  case  Dr.  Moul- 
ton reported,  asking  for  an  explanation  of  the  fact  that  it 
became  necessary  for  him  to  rotate  his  i.oo  D.  cylinders 
from  900  to  ioo°  for  each  eye,  in  order  that  the  patient 
might  have  comfort,  when  several  examinations  under  atro- 
pia  had  shown  that  the  axis  of  each  cylinder  should  be  at 
900.  My  explanation,  published  in  connection  with  his  let- 
ter, was  that  there  was  insufficiency  of  the  superior  oblique 
of  the  right  eye  and  of  the  inferior  oblique  of  the  left  eye ; 
that  these  weak  muscles,  at  the  times  of  the  several  exami- 
nations, exerted  their  full  amount  of  power,  and  thus  kept 

*  See  Ophthalmic  Record,  Vol.  I,  No.  4,  1S91. 


HOW   TO    CORRECT   THEM.  IO.S 

the  best  meridians  at  900;  that  these  muscles  at  other  times, 
because  of  fatigue,  could  not  exert  the  necessary  amount  of 
power,  and  thus  allowed  their  stronger  opposing  muscles 
(the  inferior  oblique  of  right  and  superior  oblique  of  left) 
to  change  these  meridians  from  900  to  ioo°.  It  was  at  such 
a  time  as  this  that  the  Doctor  learned  that  the  axes  of  his 
cylinders  should  be  placed  at  ioo°.  Comfort  came  to,  and 
remained  with,  his  patient  as  a  result  of  this  little  procedure. 
It  was  good  practice,  and  should  be  followed  in  all  cases  of 
astigmatism  where  there  is  nonsymmetrical  insufficiency  of 
the  obliques. 

In  symmetrical  insufficiency  of  the  obliques,  the  case  is 
very  different  in  both  principle  and  practice.  It  is  for  this 
latter  condition  that  I  am  now  able  to  point  out  the  remedy. 

To  illustrate  clearly  the  principle  and  practice,  I  will  take 
up  for  study  the  case  of  J.  B.  M.,  age  thirty-five,  whose  case 
I  was  studying  the  moment  the  thought  of  the  cure  came  to 
me.  Two  years  ago  he  came  to  consult  me  about  a  head- 
ache that  for  a  long  time  had  troubled  him,  and  which  was 
growing  more  severe.  He  had  been  advised  that  it  was 
probably  due  to  eye-strain;  and,  if  so,  it  could  be  cured  by 
properly  adjusted  lenses.  A  preliminary  examination  showed 
only  a  slight  error  of  refraction.  This  he  consented  to  have 
corrected,  hoping  that  he  would  get  relief,  other  means  hav- 
ing failed.  Under  homatropine  the  following  correction 
was  given: 


Io6  INSUFFICIENCIES    OF   THE    OBLIQUE    MUSCLES." 

O.  D.  V.  =  |°  with  -f  .25  C  +  -25  cyl.  ax.  1550. 

O.  S.  V.  =  I"  with  +  .25  O  +  -50  cyl.  ax.  900. 

It  was  determined,  at  the  same  time,  that  he  had  y2°  left 
hyperphoria.  It  was  also  determined  that  he  had  insuffi- 
ciency of  both  right  and  left  superior  obliques.  He  was  told 
that  all  but  the  latter  could  be  corrected ;  that  he  would  get 
some,  but  not  complete,  relief  by  wearing  his  sphero-cylin- 
drical lenses,  the  left  ground  on  a  prism  of  y2°  base  down; 
that,  at  times,  the  insufficiency  of  the  obliques  would  give 
him  trouble,  for  there  was  nothing  that  could  be  done  for  this 
condition.  I  did  tell  him  that  if  he  felt  a  headache  coming  on, 
when  engaged  in  near  work,  he  might  cover  one  eye  with  a 
flap,  thus  doing  away  with  the  strain  necessary  for  harmoni- 
ous action  of  the  muscles  of  the  two  eyes.  This  he  tried 
occasionally,  but  found  it  very  inconvenient  to  work  with 
one  eye  only.  His  attacks  of  suffering  were  greatly  lessened 
in  both  frequency  and  severity  for  some  months,  as  a  result 
of  the  elimination  of  some  of  the  factors  formerly  constitut- 
ing in  part  the  cause  of  his  suffering. 

He  wore  his  spectacles  continually;  but  after  awhile  his 
headaches  began  to  return.  They  grew  more  frequent  and 
more  severe  until  he  became  an  almost  daily  sufferer.  Not 
infrequently,  on  going  home  from  his  office,  his  wife  would 
have  to  put  him  to  bed  like  a  child.  He  would  occasionally 
take  medicines  prescribed  by  his  family  physician  to  relieve 
the  severity  of  the  attack.     At  intervals,  during  the  whole 


-% 


V 


HOW  TO   CORRECT   THEM.  IO7 

time,  he  would  consult  me.  When  complaining,  I  would  tell 
him  that  I  believed  that  the  then  active  cause  was  the  insuffi- 
ciency of  his  superior  obliques;  and  that  I  was  powerless  to 
do  more  than  I  had  already  advised. 

A  few  months  ago  I  made  a  second  examination  of  his 
eyes  under  the  influence  of  homatropine,  but  only  to  find 
that  the  result  of  my  former  examination  was  correct.  I  did 
not  have  to  urge  him  to  wear  his  glasses,  because  he  had 
learned  that  he  was  more  comfortable  with  than  without 
them. 

On  the  13th  of  May,  1892,  he  came  to  me  and  said  that  I 
must  do  something  for  him ;  that  he  must  have  relief.  Re- 
minding him  that  I  had  twice  investigated  his  eyes  and  each 
time  had  found  the  same  conditions  and  had  corrected  all 
that  was  correctable,  I  told  him  I  was  willing  to  try  again; 
but  that  I  was  as  unable  to  correct  the  insufficiency  of  his  ob- 
liques as  I  ever  was.  In  the  course  of  this  conversation,  I  told 
him  that,  if  he  had  but  one  eye,  he  would  not  be  a  sufferer. 
Deciding  that  it  would  be  four  days  before  he  could  return 
for  another  examination,  he  went  away.  On  the  17th,  at  the 
hour  appointed,  he  came;  and,  without  hope  of  finding  an 
additional  means  of  relief,  I  undertook  the  investigation 
again.  The  results  of  former  examinations,  as  to  lenses, 
were  confirmed. 

My  study  of  the  recti  muscles  resulted  as  formerly  in  find- 
ing a  left  hyperphoria  of  %°.     With  the  remark,  "  We  will 


Io8  INSUFFICIENCIES    OF   THE   OBLIQUE   MUSCLES: 

now  look  into  that  incorrectable  condition,"  I  began  to  in- 
vestigate the  obliques.  Placing  the  6°  double  prism  before 
his  right  eye,  the  left  eye  (the  one  under  test)  showed  the 
middle  line  dipping  unmistakably  to  the  right,  as  in  Figure 
i,  thus  showing  insufficiency  of  the  left  superior  oblique. 
Transferring  the  double  prism  to  the  left  eye,  the  right  eye 
showed  the  middle  line  dipping  to  the  left,  as  in  Figure  3, 
thus  showing  insufficiency  of  the  right  superior  oblique. 
Having  stated  again  that  nothing  more  could  be  done  for 
him,  in  the  next  moment  the  thought  occurred  to  me  that,  if 
a  cylinder  was  placed  before  the  eye  in  such  a  way  as  to 
make  the  line  incline  still  more  in  the  same  direction,  on  re- 
moving the  double  prism  the  weak  obliques  would  have  to 
act  more  than  usual  in  binocular  vision.  I  reasoned  that 
this  overaction,  being  in  the  nature  of  gymnastic  exercise,  if 
conducted  properly,  must  develop  the  weak  muscles,  and 
thus  be  a  source  of  relief  to  the  patient.  Leaving  the  dou- 
ble prism  in  front  of  the  right  eye,  I  placed  a  +  2.00  cylinder 
before  his  left.  Revolving  it  so  as  to  bring  its  axis  to  1350, 
the  middle  line  was  seen  to  dip  very  much  more  to  the  right. 
I  then  turned  the  axis  back  to  900,  when  the  dipping  was  the 
same  as  when  no  cylinder  was  on.  Turning  the  axis  of  this 
cylinder  to  450,  the  middle  line  was  made  parallel  with  the 
other  two  (this  little  procedure  of  placing  the  axis  of  a  cyl- 
inder obliquely,  first  in  one  direction,  then  in  the  other,  and 
watching  the  effect  on  the  middle  line,  will  establish  or  dis- 


HOW  TO    CORRECT   THEM.  IO9 

prove  the  correctness  of  the  diagnosis).  The  diagnosis  made 
and  positively  confirmed,  I  at  once  commenced  the  gymnas- 
tic exercise  by  placing  a  -f-  2.00  cylinder  before  each  eye, 
the  axis  of  the  right  at  700  and  the  axis  of  the  left  at  no°. 
The  patient  was  asked  to  fix  his  vision  on  a  light  twenty 
feet  distant  (the  double  prism  had  been  removed).  In  three 
minutes  the  axis  of  the  right  cylinder  was  turned  to  6o°  and 
that  of  the  left  to  1200;  three  minutes  later  the  axis  of  right 
was  placed  at  500  and  that  of  left  at  1300;  and  again  in  three 
minutes  the  axes  were  changed,  the  right  to  450  and  the  left 
to  135°-  With  each  turning  there  was  additional  demand 
made  on  the  superior  obliques,  the  maximum  being  reached 
when  the  axes  were  respectively  at  450  and  1350.  With  each 
turn  the  patient  could  feel  additional  strain.  The  cylinders 
were  allowed  to  remain  in  this  position  of  maximum  effect 
three  minutes,  when  they  were  removed  and  the  double 
prism  test  was  applied.  There  was  now  the  slightest,  if  any, 
dipping  of  the  middle  line.  Both  patient  and  practitioner 
felt  encouraged.  He  has  returned  daily  for  the  exercise, 
which  has  been  conducted  every  time  in  the  manner  above 
described. 

On  the  day  after  the  first  exercise  he  resumed  his  office 
work,  which  requires  almost  continuous  near  use  of  his  eyes, 
and  has  been  absolutely  comfortable  up  to  this  time  (the  end 
of  the  eleventh  day),  and  not  one  dose  of  medicine  has  been 
taken.    For  the  last  three  days,  before  beginning  the  exercise, 


IIO  INSUFFICIENCIES    OF  THE  OBLIQUE   MUSCLES: 

the  test,  when  applied  to  either  eye,  showed  but  little  want  of 
parallelism  of  the  lines.  His  improvement  has  been  rapid 
and  remarkable. 

I  have  now  under  the  exercise  treatment  a  little  girl,  age 
fifteen  years,  whose  trouble  is  insufficiency  of  the  inferior 
obliques.  The  dipping  of  the  middle  line  is  to  the  left  in 
the  left  eye,  and  to  the  right  in  the  right  eye,  just  the  con- 
trary of  what  was  found  in  the  other  case. 

The  exercise  in  her  case  is  carried  on  by  revolving  spas- 
modically the  axis  of  the  right  cylinder  from  900  to  1350  and 
that  of  the  left  from  900  to  450,  the  reverse  of  the  plan  in  the 
first  case.  She  does  not  bear  the  exercise  so  well  as  the  first 
patient,  but  her  improvement  in  five  days  is  noticeable. 

My  records  for  the  past  two  years  show  a  number  of  cases 
of  symmetrical  insufficiency  of  the  obliques,  to  all  of  whom  I 
stated:    "  For  this  condition  I  can  do  nothing." 

The  condition  is  real,  the  treatment  is  rational,  and  relief 
must  follow.  The  condition  is  easy  of  detection,  and  the  in- 
sufficient muscle  can  be  quickly  located.  [In  making  the 
test,  the  line,  the  double  prism,  and  the  plane  of  the  centers 
of  direction  of  the  two  eyes  should  all  be  parallel.  Observ- 
ing this  rule,  no  error  of  diagnosis  is  possible.  J  The  double 
prism  before  the  right  eye,  the  middle  line  is  seen  by  the  left 
(the  one  under  test);  if  it  dips  toward  the  opposite  (right) 
side,  the  superior  oblique  is  insufficient  (see  Figure  1);  if 
toward  the  same  side,  the  inferior  oblique  is  insufficient  (see 


HOW   TO    CORRECT   THEM.  Ill 

Figure  2).  The  same  is  true  when  the  right  eye  is  under 
test,  as  is  shown  in  Figures  3  and  4.  In  the  treatment,  either 
concave  or  convex  cylinders  can  be  used.  If  the  concave  are 
used,  and  the  insufficiency  is  in  the  superior  obliques,  the 
axes  must  be  placed  in  the  lower  nasal  quadrant;  if  in  the  in- 
ferior obliques,  then  the  axes  must  be  placed  in  the  lower 
temporal  quadrant.  If  for  the  exercise  the  convex  cylinders 
are  chosen,  the  axes  must  be  placed  in  the  lower  temporal 
quadrant  for  insufficiency  of  the  superior  obliques,  and  in 
the  lower  nasal  quadrant  for  insufficiency  of  the  inferior 
obliques.  In  either  case,  the  effect  is  increased  as  the  axes 
are  made  to  move  from  the  vertical  to  the  point  of  maximum 
effect,  which  is  450  from  the  vertical. 

The  exercise  may  be  commenced  with  a  .50  to  a  1.00  D. 
cylinder,  and'  increased  each  day  a  .50  D.,  up  to  3.00  D. 
The  cases  wall  be  very  rare  that  will  require  a  stronger  ex- 
ercise cylinder  than  the  last  named.  The  graduated  exercise 
should  be  continued  daily.  Each  eye  being  affected,  the 
exercise  cylinders  should  be  placed  before  both. 


Since  the  publication  of  the  above  paper,  my  experience 
has  confirmed  me  in  the  belief  of  the  correctness  of  its  teach- 
ings. My  first  case  continued  to  do  well,  and  for  some 
months  has  shown  no  evidence,  either  by  the  dipping  of  the 
middle  line  or  by  suffering,  that  there  is  any  insufficiency  of 
his  obliques.     He  has  continued  to  use  his  exercise  cylinders 


112  INSUFFICIENCIES    OF   THE  OBLIQUE   MUSCLES: 

from  the  beginning  to  the  present;  and  that,  too,  in  the  face 
of  my  advice  to  discontinue  them  several  months  ago.  His 
idea  in  continuing  the  exercise  (for  several  months  only  once 
a  week)  is  to  keep  the  muscles  strong.  I  have  told  him  that 
too  much  exercise  might  reverse  his  trouble ;  but  in  his  case 
nothing  of  the  kind  has  occurred. 

What  is  true  of  this  first  case  is  true  of  more  than  300  ad- 
ditional cases  that  have  been  treated  or  are  now  under 
treatment.  Experience  has  taught  me  that  patients  having 
well-marked  insufficiency  of  the  obliques  should  exercise 
twice  a  day  for  two  months,  once  a  day  for  another  two 
months,  three  times  a  week  for  a  month,  and  once  a  week 
for  another  month.  If  I  cannot  see  the  patients  to  ap- 
ply the  test,  I  take  it  for  granted  that  they  are  cured  at  the 
end  of  six  months.  Usually  the  reports  from  such  patients 
show  a  gradual  diminution  of  symptoms,  as  to  duration  and 
severity,  until  finally  there  are  no  symptoms.  Some  get 
complete  relief  very  soon  after  beginning  the  exercise ;  but 
such  are  always  advised  to  continue  through  several  months. 
If  other  ocular  errors  exist,  they  of  course  receive  attention. 

The  cylinders  I  most  frequently  use  are  -j-  1.50.  The 
great  majority  of  cases  are  better  treated  with  these  than 
with  weaker  or  stronger  cylinders.  Very  slight  cases  should 
have  weaker  cylinders ;  while  there  are  a  few  in  whom  the 
trouble  is  sufficiently  great  to  require  stronger  cylinders, 
even  a  -f-  3.00.     One  case  has  been  reported  to  me  that  re- 


HOW  TO    CORRECT   THEM.  113 

quired,  during  a  part  of  the  treatment,  -f-  6.00  cylinders. 
As  a  rule  I  do  not  find  it  necessary  to  increase  or  decrease 
the  strength  of  the  cylinders  in  the  course  of  the  treatment. 

Soon  after  beginning  the  exercise  treatment  on  my  first 
patient,  it  occurred  to  me  that  there  should  be  contraction 
and  relaxation  alternating,  in  order  to  the  more  rapid  and 
effective  development  of  the  muscles.  At  first  I  directed  my 
patients  to  look  at  the  light  through  the  cylinders  for  a  few 
seconds,  and  then  close  the  eyes  for  the  same  length  of 
time.  I  soon  learned,  however,  from  a  study  of  the  recti 
muscles,  that  a  relaxation  of  the  ocular  muscles  does  not 
come  quickly  when  the  eyes  are  closed.  To  get  rhythmic 
contraction  and  relaxation,  I  now  direct  my  patients  to  look 
at  the  light  five  seconds  through  the  cylinders;  then  look  at 
the  same  light  five  seconds  without  the  cylinders. 

For  the  benefit  of  those  who  are  interesting  themselves  in 
the  study  of  "  insufficiencies  of  the  oblique  muscles  and  how 
to  correct  them,"  I  publish  below  cuts  of  frames  which  I 
have  devised  and  use  in  my  practice,  prescribing  the  same  al- 
most daily.  The  frames  are  made  of  German  silver,  with 
circular  rims  for  the  lenses.  These  rims  are  deeply  grooved 
to  allow  a  free  rotation  of  the  lenses.  The  rims  are  marked 
at  points  15  degrees  apart,  from  900  to  450,  in  either  the 
lower  temporal  or  lower  nasal  quadrant,  depending  on  the 
pair  of  muscles  affected.     The  cylinders  used   are  usually 

+  1.50  D.,  and  the  axis  of  each  is  plainly  marked  as  shown 
8 


ii4 


INSUFFICIENCIES    OF   THE   OBLIQUE   MUSCLES 


in  the  cuts.     The  frames  are  not  marked  nor  are  the  cylin- 
ders cut  except  by  the  oculist's  order. 

Figure  i  represents  a  pair  of  exercise  cylinders  ordered 
for  a  patient's  own  use  whose  superior  obliques  are  insuffi- 
cient. The  rims,  as  shown,  are  marked  in  the  lower  tem- 
poral quadrant,  at  four  points  15  degrees  apart,  three  of 
which  are   numbered    1,    2,    and   3.     The   cylinders,  whose 


Figure  i. 


axes  are  distinctly  marked,  can  be  readily  revolved.  The 
patient  is  directed  to  place  the  mark  on  each  lens  at  the 
notch  marked  1.  Placing  them  now  before  her  eyes,  she  is 
instructed  to  look  at  a  broad  lamp  blaze,  10  to  20  feet 
distant,  for  5  seconds,  then  without  for  5  seconds,  then 
again  with  for  5  seconds,  and  so  on,  for  5  minutes.  Now 
the  two  lenses  are  to  be  revolved  so  that  their  marks  coin- 
cide with  No.  2  notch  on  rim.     The  flame  is  now  looked  at 


4 
HOW  TO    CORRECT   THEM.  115 

as  above,  for  3  minutes;  when  the  last  change  in  position  of 
lenses  is  made  by  revolving  their  marks  to  notch  No.  3,  the 
point  of  maximum  action.  The  patient  now  looks  at  the 
light,  as  above,  for  two  minutes,  which  ends  the  exercise  for 
that  day — 10  minutes  in  all. 

Figure  2  shows  the  marking  of  rims  when  the  patient  has 
insufficiency  of  the  inferior  obliques,  the  exercise  lenses  to 


Figure  2. 
be  -f-  cylinders.  The  revolution  is  made  in  the  direction  of 
the  notching  in  both  classes  of  cases.  The  points  at  which 
to  stop  and  the  time  to  look  at  the  light  are  all  the  same. 
Insufficiency  of  the  inferior  obliques  is  far  less  common  than 
that  of  the  superior  obliques. 

The  frames  should  be  so  made  that  the  lenses  will  be 
properly  centered.  There  is  no  patent  on  them,  therefore 
any  manufacturer  may  make  them. 


Il6  INSUFFICIENCIES   OF   THE  OBLIQUE   MUSCLES: 

While  in  attendance  on  the  Pan-American  Medical  Con- 
gress, it  was  suggested  to  me  by  Dr.  Swan  M.  Burnett  that, 
in  at  least  some  cases,  the  action  of  the  superior  and  infe- 
rior recti,  because  of  the  nature  of  their  scleral  attachment, 
might  throw  an  undue  amount  of  strain  on  the  oblique  mus- 
cles. As  is  well  known,  the  contraction  of  the  inferior  rec- 
tus not  only  directs  the  visual  axis  down,  but  also  rotates 
the  vertical  meridian  of  the  cornea  out.  The  same  action, 
with  the  same  results,  occurring  in  the  fellow  eye,  there 
would  be  a  divergence  of  these  meridians  above,  unless  coun- 
teracted by  the  superior  obliques.  The  superior  recti  di- 
rect the  visual  axes  up  and  rotate  the  vertical  meridians  so 
that  they  converge  above.  The  latter  result  must  be  coun- 
teracted by  the  inferior  obliques.  In  either  case,  the  attach- 
ment of  the  superior  and  inferior  recti  might  be  such  as  to 
demand  too  much  action  on  the  part  of  the  obliques,  though 
intrinsically  strong.  It  seems  to  me  that  this,  as  a  reasonable 
factor,  may  enter  into  the  causation  of  symmetrical  insuffi- 
ciency of  the  obliques.  The  fact  that  we  call  into  action 
the  inferior  recti  more  frequently  than  we  do  the  superior 
(we  look  down  more  than  we  look  up),  associated  with  the 
other  fact  that  insufficiency  of  the  superior  obliques  is  far 
more  common  than  insufficiency  of  the  inferior  obliques, 
leads  me  to  look  with  still  more  favor  on  the  thought  sug- 
gested by  Dr.  Burnett.  Still  I  believe  that  there  are  many 
cases  of  insufficiency  of  the  obliques  due  to  intrinsic  weak- 


HOW    TO   CORRECT    THEM.  117 

ness  of  these  muscles.     Often  the  two  factors  may  be  asso- 
ciated as  a  cause. 

On  hearing  Dr.  Burnett's  suggestion  I  at  once  responded: 
"  If  you  are  correct,  some  cases  of  insufficiency  of  the  ob- 
liques can  be  cured  by  dividing  the  offending  fibers  of  the 
inferior  (or  superior)  recti." 

It  seems  to  me  that  we  may  be  able  to  determine  this  mat- 
ter by  varying  our  method  of  investigation.  When,  in  a 
given  case,  the  card  and  double  prism  being  so  held  that  the 
visual  axes  are  horizontal,  there  is  no  dipping  of  the  middle 
line,  if,  on  changing  the  test  so  that  the  visual  axes  point  a 
few  degrees  below  the  horizontal  plane,  the  middle  line 
should  dip  toward  the  opposite  side,  showing  insufficiency 
of  the  superior  obliques,  it  would  appear  that  the  cause  ex- 
ists in  the  inferior  recti. 

Whether  the  cause  of  insufficiency  of  the  obliques  be 
simple  or  complex,  my  experience  leads  me  to  believe  that 
these  cases  can  all  be  cured  by  the  method  of  developing 
the  obliques  as  set  forth  in  this  chapter.  Even  when  it  can 
be  proven  that  the  inferior  recti  enter  into  the  causation  of 
insufficiency  of  the  superior  obliques,  the  effort  should  first 
be  made  to  cure  by  the  exercise  of  the  latter;  should  this 
fail,  then  a  well-directed  operation  on  the  offending  fibers 
of  the  inferior  recti  might  be  done. 


In  commenting  on  this   chapter  (Chapter  II.  in  the  first 


Il8  INSUFFICIENCIES    OF  THE    OBLIQUE    MUSCLES: 

and  second  editions  of  this  book),  critics  have  differed 
widely.  Some  have  claimed  that  they  have  not  been  able  to 
discover  the  condition  in  a  single  case;  while  others,  among 
whom  is  Dr.  Eaton,  claim  that  the  phenomena  might  be 
brought  out  in  almost  all  cases.  So  common  did  this  latter 
class  find  the  condition  that  they  pronounced  it  to  be  normal. 
Between  these  two  extremes  is  to  be  found  the  truth.  Not 
more  than  twenty-five  per  cent,  of  cases,  the  double  prism 
being  used,  will  show  insufficiency  of  the  superior  obliques; 
while  less  than  one  per  cent,  will  show  insufficiency  of  the 
inferior  obliques.  Within  the  past  few  months  a  most  re- 
markable case  of  insufficiency  of  the  inferior  obliques  has 
been  observed.  So  marked  was  the  dipping  of  the  middle 
line  toward  the  corresponding  side  that  it  took  a  plus  6.00 
cylinder,  revolved  through  an  arc  of  450  from  the  vertical, 
to  parallel  the  lines.  As  great  as  was  this  error,  the  patient 
had  not  suffered  at  any  time  much  inconvenience  in  reading 
or  writinsf,  which  of  course  was  done  below  the  horizontal 
plane.  Anything  like  this  quantity  of  insufficienc}^  of  the 
superior  obliques  would  have  rendered  her  wholly  incapable 
of  any  comfortable  seeing,  even  in  the  horizontal  plane. 

Soon  after  beginning  the  treatment  of  the  obliques,  and 
before  Dr.  Wilson  had  written  his  criticism  of  my  method 
of  treatment,  I  had  observed  that  some  patients  did  not  im- 
prove, while  others  had  marked  improvement.  Some  pa- 
tients even  got  worse  under  the  treatment.     On  investigating 


HOW  TO   CORRECT   THEM.  HO. 

these  cases  it  was  soOn  brought  out  that  those  who  were  not 
improving  were  exercising  their  eyes  while  looking  at  the 
blaze  of  a  candle ;   while  those  that  improved  most  rapidly 
exercised  while  looking  at  a  broad  lamp  blaze.     From  that 
time  on  I  directed  that  all  patients  should  use  the  broad  lamp 
blaze  when  exercising,  and  never  the  pointed  blaze  of  a  can- 
dle.    It  is  certainly  true  that  artificial  oblique  astigmatism  will 
call  into  action  either  the  superior  or  inferior  obliques,  de- 
pending on  the  character  of  the  blaze  looked  at.     The  plus 
cylinders  revolved  in  the  lower  temporal  quadrant,  intended 
for    exercising   the    superior    obliques,  will  unquestionably 
call  into  action  the  inferior  obliques  if  there  is  more  of  the 
vertical  area  of  the  retina,  than  of  the  horizontal,  impressed 
by  the  image  of  the  light.     This  is  exactly  what  would  oc- 
cur if    the    candle   were   used.     For   this   reason  the  word 
"  candle,"  wherever  it  appeared  in  this  chapter  in  former 
editions,   has  been  stricken  out.     Better  still  than  a  broad 
lamp  blaze  is  a  horizontal  slit  in  an  opaque  metal  chimney. 
The   chimney,  bright  within  and  dark  without,  should  be 
rectangular,  and  should  be  made  large  enough  to  lit  over  an 
Argand  burner,  or  even  a  large  lamp  chimney.     The  slit 
should  be  long,  and  perfectly  horizontal.      It  might  vary  in 
width  from  an  eighth  to  a  quarter  of  an  inch.     Looking  at 
this  slit  through   the  plus  cylinders,  revolved  in  the  lower 
temporal  quadrant,  would  call  into  action  only  the  superior 
obliques;   while  the  same  cylinders,  revolved  in  the  lower 


120  INSUFFICIENCIES   OF   THE   OBLIQUE   MUSCLES: 

nasal  quadrant,  the  patient  looking  at  the  same  horizontal 
streak  of  light,  would  call  into  action  the  inferior  obliques. 

Careful  observation  will  serve  to  convince  any  investigator 
of  the  fact  that  there  is  such  a  thing  as  insufficiency  of  the 
oblique  muscles.  A  careful  study  of  the  cases  in  which  this 
condition  is  found  will  show  that  at  least  a  part  of  the  nerv- 
ous phenomena  which  they  exhibit  is  dependent  on  the  exist- 
ence of  this  condition.  Two  evidences  may  be  observed  as 
to  the  good  effect  of  the  treatment  of  insufficiency  of  the  ob- 
liques, as  set  forth  in  this  chapter:  the  one,  a  parallel  condi- 
tion of  the  three  lines  when  under  the  double  prism  test,  a 
revolution  of  the  proof  cylinders  in  either  the  one  direction 
or  the  other  from  the  vertical,  through  an  arc  of  50,  causing 
the  middle  line  to  dip  either  to  the  right  or  to  the  left.  The 
other  evidence  is  that  the  patient  gets  relief  from  the  nervous 
symptoms  which  had  depended  on  the  existence  of  this  mus- 
cle error.  However  many  ocular  errors  may  be  found  in 
any  one  case,  the  operator,  guided  by  the  proper  indications, 
should  feel  it  his  duty  to  treat  them  all. 

If  what  is  taught  in  the  first  four  chapters  of  this  book  is 
false,  then  the  teaching  of  this  chapter  cannot  be  correct,  so 
far  as  the  treatment  of  the  obliques  is  concerned ;  neverthe- 
less it  would  remain  a  fact  that  there  is  such  a  condition  as 
insufficiency  of  the  obliques.  But  if  the  teaching  of  these 
four  chapters  is  correct,  then  not  only  is  the  teaching  of  this 
chapter  correct  as  to  the  existence  of  insufficiency  of  the  ob- 


HOW  TO   CORRECT   THEM.  121 

liques,  but  it  is  also  correct  as  to  the  treatment  of  this  condi- 
tion. If  natural  astigmatism  calls  into  activity  either  the  su- 
perior or  inferior  obliques,  the  meridians  of  greatest  curvature 
diverging  or  converging,  then  the  production  of  artificial  as- 
tigmatism must  be  able  to  do  the  same  thing.  The  making 
and  unmaking  of  artificial  oblique  astigmatism  will  call  into 
rhythmic  contraction  and  relaxation  either  the  superior  or 
inferior  obliques,  as  may  be  desired  by  the  operator. 
A  New  Method  of  Testing  the  Obliques. 

One  of  the  easiest,  quickest  and  surest  tests  for  insuf- 
ficiency of  the  oblique  muscles  is  by  means  of  the  Wilson 
phorometer.  The  rotary  prisms  should  be  placed  for  test- 
ing sursum-  and  deorsum-duction.  The  rotating  of  the 
prisms  should  be  continued  beyond  the  strength  of  the  mus- 
cle to  prevent  diplopia.  If  the  sursum-duction  is  30,  the  ro- 
tation should  be  carried  to  40  or  even  50.  The  false  line 
will  appear  above  the  true  one,  but  will  be  parallel  with  it 
if  the  inferior  oblique  is  sufficiently  strong  to  counteract  the 
torsion  effect  of  the  acting  superior  rectus.  By  reversing  the 
action  of  the  prisms,  the  two  lines  will  be  simultaneously 
fused  throughout  their  entire  length.  Should  the  inferior 
oblique  be  weak,  the  false  line  being  seen  by  the  left  eye, 
the  two  lines  will  converge  at  the  left ;  and  the  left  ends  of 
the  two  lines  will  fuse  first,  when  the  rotation  of  the  prisms 
is  reversed. 

If  the  displacement  is  such  as  to  call  into  action  the  in- 


122  INSUFFICIENCIES    OF   THE   OBLIQUE   MUSCLES: 

ferior  rectus,  when  carried  far  enough  to  cause  diplopia,  the 
false  line  (the  lower)  will  be  parallel  with  the  other,  if  the 
superior  oblique  is  strong  enough  to  counteract  the  torsion 
effect  of  the  acting  inferior  rectus ;  but  if  the  oblique  is  not 
strong  enough  to  accomplish  this  result,  the  two  lines  will 
converge  at  the  left.  Reversing  the  action  of  the  prisms, 
the  left  ends  of  these  lines  will  fuse  first.  In  my  own  case 
the  lines  are  parallel  when  the  false  one  is  above,  but  con- 
verge at  the  left  distinctly  when  the  false  line  is  made  to  ap- 
pear below.  Reversing  the  action  of  the  prisms,  when  the 
false  line  is  above,  the  two  fuse  throughout  at  the  same  mo- 
ment; but  when  the  first  line  is  below,  fusion  of  the  left 
ends  takes  place  first.  Just  the  reverse  is  true  in  Dr.  G.  H. 
Price's  case. 

The  test  can  be  made  both  in  the  far  and  the  near.  If  the 
distant  test  should  show  no  leaning  of  the  false  line,  but  the 
near  test  should  reveal  it,  at  once  suspicion  of  error  of  at- 
tachment of  the  intetni  would  occur.  Such  error  of  attach- 
ment of  the  interni  would  not  only  converge  the  visual 
axes,  but  would  also  effect  torsion  in  one  direction  or  the 
other,  which  would  manifest  itself  or  not,  depending  on  the 
quantity  of  the  corrective  power  of  the  obliques. 

Dr.  Maddox,  of  Edinburgh,  was  the  first  to  call  attention 
to  the  delicacy  of  the  test  of  the  obliques  by  means  of  re- 
volving a  single  prism,  which  had  caused  vertical  diplopia,  in 
such  a  way  as  to  fuse  the  two  lines.     Insufficiency  of  the  ob- 


HOW  TO   CORRECT   THEM.  I2S 

liques  will  allow  fusion  at  one  end  first.  When  the  base  of 
the  prism  was  down,  its  revolution  tested  the  inferior  ob- 
lique'; when  the  base  was  up,  its  revolution  tested  the  su- 
perior oblique,  a  statement  not  made  by  Dr.  Maddox. 

The  delicacy  of  the  test  of  the  obliques  by  the  Wilson 
phorometer  will  no  doubt  show  a  larger  per  cent,  of  cases 
of  insufficiency  of  both  the  superior  and  inferior  obliques 
than  could  be  found  by  the  double  prism  test. 

All  the  cases  thus  found  need  not  be  treated.  If  in  both 
the  sursum  and  deorsum  tests,  the  superior  obliques  should 
show  weakness  by  the  false  line,  when  above,  leaning  to  the 
opposite  side,  but  not  to  so  great  an  extent  as  when  below, 
certainly  these  muscles  should  be  strengthened  by  exercise. 
On  the  other  hand,  when  the  false  line  is  below  and  inclines 
toward  the  corresponding  side,  though  not  so  much  as  when 
above,  the  indication  for  treating  the   inferior  obliques  is 

strong. 

I  have  not  seen  such  a  case,  but  I  believe  it  possible  for 
the  false  line  to  incline  in  one  direction  when  above,  and  in 
the  opposite  direction  when  below  the  true  line,  thus  clearly 
showing  insufficiency  of  both  the  superior  and  inferior  ob- 
liques. This  might  be  so  great  as  to  require  the  exercise  of 
each  pair  (the  two  superior  being  counted  a  pair  and  like- 
wise the  two  inferior)  at  least  once  in  the  twenty-four  hours. 
Such  a  condition  of  the  obliques  would  be  like  asthenic  or- 
thophoria. 


CHAPTER  VI. 

RELATIONSHIP      BETWEEN     THE     CENTERS     OF 
ACCOMMODATION  AND  CONVERGENCE. 

That  there  is  a  relationship  between  accommodation  and 
convergence  has  long  been  taught;  but  the  full  extent  of 
this  relationship  and  its  consequences  have  not,  to  the  pres- 

« 

ent,  been  fully  set  forth  in  an}T  published  work.  There  is 
more  in  it  than  the  simple  fact  that,  for  every  degree  of  con- 
vergence, there  is  a  corresponding  activity  of  the  accommo- 
dation. In  a  pair  of  emmetropic  and  orthophoric  eyes  this 
is  probably  all,  and  it  is  enough;  but  in  the  many  eyes  not 
thus  happily  conditioned  there  is  much  more  than  this  de- 
pendent on  the  intimate  relationship  between  these  two  cen- 
ters. 

There  is  no  study  more  interesting  than  that  of  the  nuclei 
(the  centers)  beneath  the  aqueduct  of  Sylvius  and  in  the 
floor  of  the  fourth  ventricle ;  and  of  these  centers  not  the 
least  in  interest  is  the  study  of  the  oculo-motor  center,  the 
one  first  in  position  and  first  in  importance.  It  is  the  largest 
of  these  centers,  and  itself  is  the  home  of  several  centers. 
As  a  whole  we  may  speak  of  it  as  controlling  the  sphincter 

of  the  iris,  the  muscle  of  accommodation,  the  internal  rec- 

(124) 


ACCOMMODATION    AND    CONVERGENCE.  1 25 

tus,  the  superior  and  inferior  recti,  and  the  inferior  oblique; 
but  for  each  of  these  muscles  there  is,  in  this  nucleus,  an  in- 
dividual center,  the  first  three  of  which — viz.,  that  for  the 
sphincter  of  the  iris,  that  of  accommodation,  and  that  of  con- 
vergence— are  so  intimately  related  that,  when  one  is  excited 
into  activity,  the  other  two  either  act  or  stand  ready  for  ac- 
tion. All  of  the  centers  of  the  oculo-motor  nucleus  have 
one  common  master,  which  is  the  guiding  sensation  residing 
in  the  retina,  its  home  being  the  macula  lutea  and  its  imme- 
diate neighborhood.  The  two  ocular  centers  (the  fourth 
and  the  sixth),  situated  farther  back,  are  also  under  the  con- 
trol of  this  same  guiding  sensation;  but  it  is  not  intended, 
in  this  paper,  to  study  these  and  their  relationship  to  each 
other  and  to  the  centers  of  the  oculo-motor  nucleus. 

The  oculo-motor  center  not  only  has  connection,  by 
means  of  nerve  fibers,  with  the  muscles  already  named,  but 
it  also  receives  fibers  from  the  retina  through  the  optic 
nerves  and  tract,  through  which  the  guiding  sensation  sends 
its  commands  or  requests.  This  center  also  has  an  intimate 
connection  with  its  fellow-center  of  the  opposite  side,  which 
enables  them  to  act  in  harmony,  although  the  one  can  never 
act  for  the  other. 

From  this  brief  study  of  the  centers  giving  motility  to  the 
eyes,  we  may  pass  on  to  a  study  of  the  two  most  intimately 
connected  centers,  the  one  of  accommodation  and  the  other 
of  convergence.     As  already  intimated,  the  whole  truth  is 


126  RELATIONSHIP    BETWEEN    THE    CENTERS 

not  embodied  in  the  statement  that,  for  every  degree  of  con- 
vergence, there  is  a  corresponding  contraction  of  the  ciliary 
muscle  (in  persons  under  45  years  of  age  and  emmetropic). 
The  following  statement  is  full  of  truth,  and  is  for  the  first 
time  made :  Whenever  one  of  these  centers  is  called  into  ac- 
tivity there  is  a  tendency  on  the  -part  of  the  other  to  become 
active  in  a  corresponding  degree.  If  the  associated  center 
does  not  put  forth  action,  it  is  because  the  guiding  sensation 
commands  it  not  to  do  so;  or  the  center  no  longer  has  its 
proper  organ  under  its  power.  In  one  of  these  ways  is  ex- 
plained the  dissociation  of  these  centers  by  prisms  affecting 
convergence,  and  by  convex  and  concave  lenses  affecting 
accommodation  ;  in  the  other  way  is  explained  the  failure  of 
the  accommodative  center  to  exhibit  activity  corresponding  to 
convergence  in  the  eyes  of  the  old,  and  in  young  eyes  that 
are  under  the  influence  of  a  mydriatic,  and  in  aphakial  eyes. 

When  prisms  are  placed  before  the  eyes,  the  bases  in, 
less  convergence  is  needed,  but  the  same  accommodation 
must  be  exercised.  It  is  only  because  of  the  imperative 
command  of  the  guiding  sensation  that  the  accommodation 
does  more  than  its  accustomed  work  for  the  degree  of  con- 
vergence exercised;  and,  too,  under  this  new  condition,  the 
unusual  activity  of  the  accommodation  excites  a  tendency  to 
greater  activity  on  the  part  of  the  internal  recti,  which  is 
kept  in  abeyance  by  the  guiding  sensation. 

When  properly  centered  convex  lenses  are  placed  before 


OF  ACCOMMODATION  AND  CONVERGENCE.        1 27 

young,  emmetropic  eyes,  while  the  patient  looks  at  a  book, 
the  two  centers  are  dissociated  in  action  but  not  in  tendency. 
Under  this  condition  the  guiding  sensation  compels  the  cil- 
iary muscle  to  relax  in  part  or  in  whole,  depending  on  the 
strength  of  the  lenses  used,  which  excites  in  the  converging 
centers  a  tendency  to  relax,  which  is  prevented  by  an  unu- 
sual demand  on  this  center  compelling  it  to  effect  the  needed 
amount  of  convergence;  and,  on  the  other  hand,  this  ex- 
cessive (proportionately)  demand  on  the  centers  of  conver- 
gence excites  a  proportionate  tendency  to  action  on  the  part 
of  the  centers  of  accommodation,  which  is  alone  restrained 
by  the  guiding  sensation. 

Again  when  properly  centered  concave  glasses  are  placed 
before  the  eyes,  there  is  dissociation  of  action  but  not  of  ten- 
dency. On  looking  at  the  page,  more  than  the  usual  amount 
of  accommodation  is  necessary  in  order  to  have  sharp  im- 
ages on  the  retinas.  This  extra  demand  on  the  accommo- 
dative centers  is  not  attended  by  a  corresponding  increase 
of  convergence,  because  the  guiding  sensation  suppresses  the 
tendency. 

Dissociation  of  accommodation  and  convergence,  in  nor- 
mal  eyes,  is  never  comfortable,  and  the  discomfort  is  due  as 
much  to  the  restraining  influence  of  the  guiding  sensation 
over  the  one  center  as  to  its  exciting  influence  over  the  other. 

When  accommodation  and  convergence  are  dissociated 
by  age,  or  by  the  continued  influence  of  a  mydriatic  on  the 


128  RELATIONSHIP    BETWEEN    THE    CENTERS 

ciliary  muscle,  or  by  the  removal  of  the  crystalline,  the  cen- 
ter of  accommodation  not  only  becomes  unable  to  influence 
the  center  of  convergence,  but  also  becomes  incapable  of 
being-  influenced  by  it.  Such  dissociation,  j)cr  sc,  is  never 
attended  by  the  discomfort  that  is  brought  about  in  dissocia- 
tion by  means  of  prisms  and  convex  and  concave  lenses. 

There  are  conditions  modifying  the  salutary  association 
of  these  two  centers,  from  which  result  phenomena  that  may 
be  clearly  understood.  There  may  be  but  one  unfavorable 
condition,  or  there  may  be  two  or  more  associated.  Of  the 
disturbing  conditions  we  may  speak  first  of 

Hypermetropia, 
simple  or  associated  with  astigmatism.  For  the  present  we 
will  consider  this  condition  as  unassociated  with  any  form  of 
heterophoria,  at  least  as  far  as  the  external  and  internal  recti 
are  concerned.  The  hypermetropia,  for  convenience  of 
study,  may  amount  to  3  D.  The  existence  of  this  error 
creates  a  demand  on  the  accommodative  centers  when 
vision  is  fixed  on  distant  objects.  The  activity  of  these  cen- 
ters, when  the  visual  lines  are  parallel,  excites  a  tendency  to 
activity  on  the  part  of  the  converging  centers,  which  is  sup- 
pressed by  the  influence  of  the  guiding  sensation  so  long  as 
the  two  eyes  are  on  their  guard;  but  let  any  one  of  the  sev- 
eral tests  for  heterophoria  be  applied,  the  guiding  sensation 
loses  its  "grip,"  and  the  tendency  to   act  is   converted  into 


OF    ACCOMMODATION    AND    CONVERGENCE.  1 29 

unrestrained  action,  and  we  have  esophoria  shown  which  has 
no  foundation  in  the  structure  or  attachment  of  the  internal 
recti.  When  these  eyes  are  used  in  near  work — at  a  dis- 
tance of  fourteen  inches — there  is  twice  the  demand  on  the  ac- 
commodative centers  that  would  be  made  were  there  emme- 
tropia.  The  excessive  excitation  of  the  accommodative  cen- 
ters is  necessarily  attended  by  a  corresponding  disposition 
for  greater  activity  on  the  part  of  the  converging  centers 
than  is  necessary  for  bringing  the  visual  axes  together  at  the 
point  looked  at ;  but  the  guiding  sensation  suppresses  enough 
of  this  tendency  to  prevent  the  axes  coming  together  at  a 
shorter  distance.  The  test  for  heterophoria  is  applied  and, 
the  guiding  sensation  having  lost  its  influence  over  the  con- 
verging centers,  esophoria  in  the  near  is  shown.  The  prac- 
tical deduction  to  be  made  from  this  observation  is  that  a 
full  correction  of  the  hyper  metropia  will  relieve  not  only  the 
focal  error,  but  the  esophoria  as  well.  The  wearing  of  these 
correcting  lenses  continuously  will  relieve,  from  the  begin- 
ning, all  asthenopic  symptoms  of  whatever  nature.  And, 
too,  this  form  of  esophoria  (pseudo-esophoria)  disappears 
when  accommodation  is  suspended  by  age. 

Again,  hypermetropia  may  be  associated  with  an 

Esophoria 

which  depends  on  an  overdevelopment  of  the  internal  recti, 

or  on  their  attachment  being  too  far  forward,  or  on  both  of 
9 


I3O  RELATIONSHIP    BETWEEN    THE    CENTERS 

these  causes  combined.  If  the  intrinsic  esophoria  is  low  in 
degree,  although  it  will  be  increased  by  the  hypermetropia, 
the  only  resulting  phenomena  will  be  asthenopic  symptoms 
of  one  kind  or  another,  the  disposition  on  the  part  of  the 
center  of  convergence  to  overact  being  restrained  by  the 
guiding  sensation.  On  the  other  hand  the  inherent  esopho- 
ria will  have  no  undue  influence  over  the  accommodative 
centers;  hence  there  is  never  found  in  such  eyes  even  a  ten- 
dency to  true  spasm  of  accommodation. 

The  practical  deduction  made  from  our  study  of  hyper- 
metropia complicated  with  inherent  esophoria,  is:  Give  a 
full  correction  of  the  hypermetropia  and,  in  that  way,  relieve 
not  only  the  focal  error,  but  also  relieve  all  of  that  part  of 
the  esophoria  not  inherent  in  the  muscles.  Should  the  re- 
maining esophoria  give  trouble,  it  must  be  corrected  by 
either  rhythmic  exercise  of  the  externi  or  by  partial  tenoto- 
mies of  the  interni,  or  by  both  procedures. 

Esophoria  depending  on  hypermetropia  solely  is  wholly 
relieved  by  advancing  years,  as  well  as  by  glasses  that  fully 
correct  the  focal  error.  It  is  also  relieved,  after  the  first 
few  hours,  by  the  use  of  a  mydriatic,  and  this  relief  contin- 
ues with  the  continued  use  of  the  drug.  A  very  peculiar 
feature  of  the  use  of  a  mydriatic  is  that,  at  first — probably 
from  one  to  several  hours — a  mydriatic,  in  hypermetropic 
eyes,  will  increase  the  esophoria,  will  lessen  an  exophoria  or 
convert  it  into  orthophoria  or  even  into  an  esophoria.     Until 


OF    ACCOMMODATION    AND    CONVERGENCE.  I3I 

now  this  has  been  unexplained;  and  the  following  explana- 
tion is  not  only  new,  but  it  must  be  true:  The  mydriatic 
acts  on  either  the  endings  of  the  accommodative  nerve  fibers, 
or  on  the  fibers  of  the  muscle  of  accommodation,  certainly 
not  on  the  accommodative  centers,  which,  therefore,  must 
remain  in  a  state  susceptible  of  excitation  by  the  demands 
from  the  guiding  sensation.  As  the  muscles  of  accommoda- 
tion pass  into  their  forced  rest,  the  retinal  images  become  less 
sharp  in  outline,  the  blurring  increasing  up  to  the  point  of 
full  suspension  of  accommodation.  The  guiding  sensation 
calls  on  the  accommodative  centers  for  sharper  images,  and 
the  impulse  is  sent  out,  but  finds  the  muscles  unresponsive; 
the  call  is  repeated  more  eagerly,  and  a  stronger  impulse  is 
sent  to  the  sleeping  muscles,  and  still  no  change  is  effected 
in  the  images ;  and  thus  the  calls  and  the  responses  are  kept 
up  for  a  longer  or  a  shorter  time.  For  every  degree  of  ac- 
tivity excited  in  the  accommodative  centers  there  is  a  corre- 
sponding tendency  to  activity  generated  in  the  converging 
centers,  which  is  kept  in  abeyance  by  the  same  guiding  sen- 
sation that  is  calling  for  action  on  the  part  of  the  accommo- 
dative centers.  So  long  as  the  calls  are  made  on,  and  re- 
sponses are  made  by,  the  accommodative  centers,  the  cen- 
ters of  convergence  stand  ready  to  call  into  unusual  action 
the  interni,  which  they  do  the  moment  the  guiding  sensation 
is  robbed  of  its  restraining  power  by  the  test  for  heterop-ho- 
ria,  when  esophoria  is  shown.     But  finally  the  guiding  sen- 


132  RELATIONSHIP    BETWEEN    THE    CENTERS 

sation  ceases  its  calls,  or,  from  exhaustion,  the  accommo- 
dative centers  cease  to  respond,  and  now  the  normal  muscu- 
lar condition  is  again  shown,  and  will  remain  manifest  al- 
though the  mydriatic  may  be  continued.  From  this  obser- 
vation on  the  mydriatic  as  a  disturber  of  the  salutary  rela- 
tionship of  the  centers  of  accommodation  and  convergence, 
we  deduce  the  following  conclusion :  A 11  tests  for  lateral  hete- 
rophoria  arc  wholly  unreliable  within  the  first  few  hours 
after  eyes  have  been  brought  under  the  influence  of  a  mydri- 
atic. 

Again,  hypermetropia  may  be  associated  with  an  intrinsic 
or  true  esophoria  of  so  high  a  degree  that,  while  the  guid- 
ing sensation  calls  into  activity  the  accommodative  centers, 
that  sharp  images  may  be  formed,  there  is  excited  in  the 
converging  centers  a  tendency  to  activity  which  cannot  be 
restrained  by  the  guiding  sensation,  and  there  results 

An  Internal  Strabismus. 
In  many  cases  of  strabismus,  the  intrinsic  esophoria  could 
be  restrained  by  the  guiding  sensation,  if  the  eyes  were  only 
emmetropic  or  even  myopic ;  but  there  being  hypermetropia 
to  excite  pseudo-esophoria,  this,  combined  with  the  true  es- 
ophoria, throws  off  the  restraining  influence  of  the  guiding 
sensation,  and  esotropia  results.  This  condition,  as  is  well 
known,  occurs  mainly  in  early  childhood,  when  accommo- 
dation is  most  powerful,  and  when  there  is  a  natural  dispo- 


OF    ACCOMMODATION    AND    CONVERGENCE.  1 33 

sition  on  the  part  of  the  child  to  hold  an  object  too  near  the 
eyes.  Many  children  with  crossed  eyes  would  never  have 
been  thus  disfigured  if  they  had  not  been  allowed  to  look  at 
thino-s  attractive  to  them,  at  too  short  a  distance  from  the 
eyes.  With  the  above  thought  in  mind  it  is  plain  to  us  how 
many  crossed  eyes  may  be  straightened,  in  early  childhood, 
by  suspending  the  accommodation  and  correcting  the  focal 
errors,  by  means  of  which  the  cause  of  the  pseudo-esopho- 
ria  is  removed,  leaving  the  true  esophoria  to  be  called  back 
into  a  state  of  suspension  by  the  guiding  sensation.  The 
practical  conclusion  reached  is  this:  Give  a  full  correction 
of  hyftermetroftia  in  all  cases  of  internal  squint.  Such  a 
correction  cannot  be  determined  without  first  bringing  into  a 
state  of  rest  the  hyper-developed  ciliary  muscles.  Without 
the  further  use  of  a  mydriatic,  many  cases  of  esotropia  can 
be  corrected  by  the  continuous  wearing  of  the  convex  lenses; 
but  there  are  many  other  cases  in  which  the  mydriatic  must 
be  used  for  a  long  while,  in  order  to  prevent  any  excitation 
of  the  accommodative  centers  in  near  seeing,  and  thereby 
completely  preventing  the  slightest  pseudo-esophoria.  It 
takes  a  mydriatic,  in  some  cases,  to  subdue  ciliary  muscles 
that  have  become  overdeveloped,  which,  in  spite  of  the  cor- 
recting lenses,  would  exert  too  much  power  in  response  to 
an  impulse  from  the  accommodative  centers,  which  impulse, 
because  of  long  habit,  itself  might  be  too  great.  This  over- 
action  (the  lenses  being  on)  has  been  falsely  termed  spasm 


134  RELATIONSHIP    BETWEEN    THE    CENTERS 

of  accommodation,  a  condition  which  can  have  no  existence 
except  as  a  result,  or  complication,  of  exophoria.  It  is  only 
a  continuance  of  a  part  of  that  action  which  was  necessary 
before  the  correcting  glasses  were  given ;  and  as  the  action, 
when  necessary,  caused  pseudo-esophoria,  the  continued  ac- 
tion, when  not  necessary,  will  likewise  cause  the  same,  hence 
the  necessity  for  the  mydriatic.  Should  the  ciliary  muscles 
become  quiet  without  a  mydriatic,  when  objects  at  a  distance 
are  made  to  throw  their  images  on  the  retinse  by  means  of 
lenses,  the  guiding  sensation  would  call  their  centers  into 
activity,  when  an  object  looked  at  is  near  by.  This  needed 
stimulation  of  the  accommodative  centers  will  excite  an  ex- 
cessive tendency  to  act  on  the  part  of  the  converging  centers, 
and  there  results  squint  in  the  near,  the  same  disappearing 
when  distant  objects  are  again  viewed.  We  conclude  then 
that,  while  some  crossed  eyes  maybe  straightened  by  glasses 
only,  it  is  better  to  aid  the  glasses,  in  all  cases,  by  the  long- 
continued  use  of  the  mydriatic.  Nor  should  the  fact  that  a 
mydriatic,  at  first,  increases  the  strabismus,  deter  any  one 
from  using  it;  for,  as  already  explained  in  this  paper,  when 
speaking  of  the  effects  of  a  mydriatic  in  cases  of  esophoria, 
exophoria,  and  orthophoria,  this  stimulating  effect  passes 
away  in  a  few  hours.  In  a  case  recently  under  our  observa- 
tion, the  increased  effect  lasted  only  an  hour,  when  the  stra- 
bismus began  to  lessen  and,  in  a  short  time,  disappeared, 
solely  as  a  result  of  the  mydriatic.     Stevens  was  the  first  to 


OF    ACCOMMODATION    AND    CONVERGENCE.  1 35 

notice  that  a  mydriatic  not  only  was  capable  of  increasing  an 
esotropia,  but  actually  produced  it  in  one  of  his  cases,  which 
he  published  but  did  not  explain.  Since  then  we  have  ob- 
served its  power  to  increase  internal  squint  in  all  our  cases, 
but  have  not  been  able  to  understand  why  until  now. 

In  the  correction  of  esotropia  by  mydriatics  and  lenses, 
the  pseudo-esophoria  has  been  destroyed,  and  the  es- 
otropia has  been  converted  into  true  esophoria,  which  must 
be  relieved  at  some  time  by  partial  tenotomies,  shortening 
of  the  external  recti,  or  by  rhythmic  exercise.  In  many  cases 
two  or  all  of  these  procedures  will  have  to  be  combined. 
Without  them  the  intrinsic  esophoria  will  remain  always  and 
be  a  perpetual  source  of  nervous  phenomena. 

Intrinsic  Exophoria 

may  be  classed  among  the  causes  of  disturbed  relationship 
between  the  centers  of  convergence  and  accommodation. 
To  prevent  crossed  diplopia,  the  inherent  power  of  the 
strong  external  recti  leads  the  guiding  sensation  to  call  the 
centers  of  convergence  into  excessive  activity.  In  this  way 
the  weak  internal  recti  counteract  the  more  powerful  externi. 
This  augmented  action  of  the  centers  of  convergence  ex- 
cites a  corresponding  tendency  to  act  on  the  part  of  the  cen- 
ters of  accommodation,  which,  in  most  cases,  is  restrained 
by  the  guiding  sensation ;  but  in  some  cases  the  tendency  to 
action  of  the  accommodative  centers,  when  the  interni  are 


I36  RELATIONSHIP    BETWEEN    THE    CENTERS 

weak,  becomes  uncontrollable  by  the  guiding  sensation,  and 
real  spasm  of  accommodation  (pseudo-myopia)  is  developed. 
The  spasm  may  be  thus  excited  in  emmetropic,  hyperme- 
tropic, or  myopic  eyes,  and  is  to  the  muscle  of  accommoda- 
tion what  esotropia  is  to  the  interni — in  each  the  guiding 
sensation  has  lost  its  power  to  control  a  tendency  excited  by 
a  disturbance  of  the  normal  relationship  between  the  centers 
of  accommodation  and  convergence. 

The  tendency  to  act  excited  in  the  accommodative  centers 
by  the  overacting  centers  of  convergence,  whether  sup- 
pressed by  the  guiding  sensation  or  not,  strengthens  the  con- 
verging centers  in  their  mastery  over  the  weak  interni,  and 
this,  too,  in  all  eyes,  whether  emmetropic,  hypermetropic,  or 
myopic.  But  whatever  may  be  thought  of  the  tendency  to 
activity  excited  in  the  centers  of  accommodation  by  over- 
taxed converging  centers,  making  the  latter  stronger,  it  can- 
not be  doubted  that  actual  ciliary  strain,  such  as  is  neces- 
sary in  hypermetropic  eyes,  does  give  to  the  converging  cen- 
ters easier  and  more  complete  control  over  the  interni.  The 
reason  for  this  has  already  been  made  clear.  Therefore 
this  reasonable  deduction  :  Hyper metr opia,  when  associated 
with  exophoria,  should  not  be  corrected  if  low  in  degree,  and 
should  be  only  partially  corrected  if  great  in  quantity.  The 
greater  the  exophoria  the  less  of  the  hypermetropia  should  be 
corrected.  The  ciliary  strain  necessary  for  the  correction 
of  1  D.  to  3  D.  hypermetropia  is  more  kindly  borne  by  the 


OF    ACCOMMODATION    AND    CONVERGENCE.  1 37 

nervous  system,  in  many  cases  of  exophoria,  than  would  be 
the  pseudo-exophoria  which  the  correcting  lenses  would  en- 
gender. Thus  there  is  a  reason  for  making  no  correction  at 
all,  or  only  a  partial  correction,  of  hypermetropia  in  certain 
cases  (the  exophoric);  while,  on  the  other  hand,  there  is 
every  reason  for  making  the  fullest  correction  in  other  cases 
(the  esophoric). 

Who  has  not  seen  one  or  many  hypermetropes  wearing 
comfortably  concave  lenses,  who  could  not  bear  the  use  of 
convex  lenses?  Such  cases  have  always  been  exophoric. 
For  the  same  reason  an  emmetrope  who  is  exophoric  could 
wear,  with  increased  comfort,  concave  glasses.  In  myopia  of 
3  D.  there  is  no  ciliary  strain  required,  hence  the  guiding 
sensation  never  makes  a  demand  on  the  center  of  accommo- 
dation. This  is  well  in  cases  of  esophoria,  so  far  as  comfort 
is  concerned;  but  in  orthophoria  and  exophoria  a  correction 
of  the  myopia  would  greatly  increase  the  comfort  of  seeing 
at  all  distances. 

As  convex  glasses  and  mydriatics  will  correct  an  esotro- 
pia, so  concave  glasses  and  myotics  should  correct  an  exo- 
tropia ;  but  as  to  the  last  statement  we  have  had  no  expe- 
rience. In  neither  case  is  the  intrinsic  muscle  error  cor- 
rected (cured) — it  is  only  held  in  abeyance  the  more  easily. 

The  first  effect  of  a  mydriatic  when  instilled  into  eyes  that 
are  hypermetropic  and  esophoric  will  be  attended  by  suffer- 
ing more  or  less  severe,  while  the  reverse  is  true  in  cases  of 


T,3S  RELATIONSHIP    BETWEEN    THE    CENTERS 

hypermetropia    associated  with    exophoria.     The   reason  is 
clear. 

The  conclusions  of  this  paper  may  be  placed  together  here : 
i.   Give  a  full  correction  of  hypermetropia  when   associ- 
ated with  esophoria. 

2.  Give  no  correction,  or  only  a  partial  correction,  of  hy- 
permetropia when  associated  with  exophoria. 

3.  Give  a  full  correction  of  myopia  when  associated  with 
exophoria,  and  when  there  is  orthophoria. 

4.  For  near  work  give  only  a  partial  correction,  or  none 
at  all,  of  myopia  when  associated  with  esophoria.  A  full 
correction  may  be  given  for  distant  seeing. 

5.  A  full  correction  of  hypermetropia  cures  a  pseudo-eso- 
phoria  in  esophoric  cases,  and  creates  a  pseudo-exophoriain 
exophoric  cases. 

6.  A  full  correction  of  myopia  cures  a  pseudo-exophoria 
in  exophoric  eyes,  and  creates  a  pseudo-esophoria  in  eso- 
phoric eyes,  when  engaged  in  near  work. 

7.  In  hypermetropia  associated  with  internal  strabismus, 
fully  correcting  lenses,  aided  by  mydriatics,  remove  all 
pseudo-esophoria  and  thus  make  it  possible  for  the  guiding 
sensation  to  resume  control  of  the  converging  centers,  in 
such  a  way  as  to  restrain  the  true  esophoria,  and  thus  cure 
the  strabismus. 

8.  In  myopia  associated  with  exotropia,  fully  correcting 
lenses,  with  myotics,  will  remove  pseudo-exophoria  and  thus 


OF    ACCOMMODATION    AND    CONVERGENCE.  1 39 

make  it  possible  for  the  guiding  sensation  to  restrain  the  true 
exophoria,  and  thereby  cure  an  external  squint. 

9.  Any  test  for  lateral  heterophoria,  within  the  first  few 
hours  after  beginning  a  mydriatic,  is  wholly  unreliable,  even 
with  lenses  on. 

The  above  conclusions  are  based  on  the  idea  that  nothing 
is  to  be  done  for  the  direct  relief  of  the  muscle  errors.  A 
better  practice  would  be  to  cure  the  heterophoric  conditions 
by  rhythmic  exercise,  when  possible,  otherwise  by  operations 
(partial  tenotomies  and  shortenings)  and  rhythmic  exercise, 
and  then  give  an  approximately  full  correction  of  whatever 
focal  error  there  may  be. 


When  this  chapter  was  written  we  had  no  knowledge 
of  the  existence  of  a  paper  by  Dr.  A.  B.  Norton,  of 
New  York,  on  the  question  "  Can  Headaches  and  Astheno- 
pia, Resulting  from  Hyperopia,  Be  Relieved  without  Glass- 
es?" Soon  after  we  had  written,  a  letter  came  from  Dr. 
Norton  calling  our  attention  to  the  fact  that  thoughts  very 
much  akin  to  those  which  we  had  embodied  had  been  pub- 
lished by  him  in  the  October,  1890,  issue  of  the  Journal  of 
Ophthalmology,  Otology  and  Laryngology.  The  first  quo- 
tation we  would  make  from  Dr.  Norton's  paper  is  as  fol- 
lows: 

"  I  do  not  wish  to  be  understood  as  making  the  claim  that 
no  case  of  hyperopia  needs  glasses,  or  that  all  cases  of  head- 


I4O  RELATIONSHIP   BETWEEN   THE    CENTERS 

aches  in  hyperopia  patients  can  be  cured  without  glasses; 
but  simply  desire  to  point  out  a  new  factor,  which,  in  my 
opinion,  renders  the  need  of  glasses  unnecessary  in  many 
cases  that  have  heretofore  been  considered  as  demanding 
their  use ;  and  further  that,  in  those  cases  in  which  the  neces- 
sity of  glasses  still  seems  to  be  imperative,  improper  glasses 
may  be  prescribed  from  a  lack  of  careful  examination  as  to 
the  condition  of  the  recti  muscles." 

The  chief  thought  which  the  Doctor  intended  to  express 
in  his  paper,  and  to  which  he  applied  the  term  "  new  factor," 
is  the  strengthening  of  the  ciliary  muscles  as  a  result  of  ex- 
ercise of  the  internal  recti.  Incidentally  he  brings  out  the 
fact  that,  in  prescribing  lenses  for  hyperopia,  the  strength 
should  be  determined,  not  wholly  by  the  quantity  of  the  de- 
fect, but  in  part  by  the  relationship  shown  to  exist  between 
the  opposing  lateral  muscles.  The  thought  that  by  increas- 
ing the  power  of  convergence  the  accommodative  power 
would  also  be  increased,  he  believes  to  be  "  supported  by 
the  fact  that  when  we  put  on  a  convex  glass  in  hyperopia, 
with  exophoria,  or  a  weakened  power  of  convergence,  we 
cause  a  greater  exophoria  with  a  diminished  incentive  to 
convergence,  and  thereby  diminish  the  power  to  converge, 
with  the  result  that  the  more  delicate  ciliary  muscle,  with 
but  a  small  fraction  of  its  full  power  still  left  unused,  is  called 
upon  to  perform  a  certain  portion  of  the  work  of  its  much 
stronger  associate  muscle,  the  internal  rectus;  and  thus,  by 


OF  ACCOMMODATION   AND    CONVERGENCE.  I4I 

increasing  the  demand  upon  an  already  weakened  muscle,  I 
believe  that  serious  harm  may  be  done." 

In  closing  his  paper  he  drew  the  following  deductions: 

"  1.  Always  examine  the  muscular  deviation  with  and 
without  the  correcting  lenses,  as  convex  glasses  will  increase 
exophoria  and  decrease  esophoria. 

"  2.  If  exophoria  exists  with  hyperopia,  always  prescribe 
the  weakest  glass  possible  or  none  at  all. 

"3.  If  esophoria  is  found  with  hyperopia,  prescribe  the 
glass  that  corrects  the  esophoria,  or  as  nearly  so  as  possi- 
ble." 

Those  wishing  to  read  all  of  Dr.  Norton's  paper  from 
which  we  have  quoted  can  find  the  same  in  the  copy  of  the 
journal  already  referred  to.  The  paper  is  richly  worth  the 
reading. 


CHAPTER  VII. 

RHYTHMIC  EXERCISE  THE  PROPER  METHOD  OF 
DEVELOPING  THE  OCULAR  MUSCLES.* 

The  development  of  the  ocular  muscles,  by  means  of  gym- 
nastic exercise,  has  received  but  little  attention  from  modern 
authors.  Noyes  devotes  about  one  page  to  the  subject;  De- 
Schweinitz,  less  than  one  page;  Schmidt-Rimpler,  three 
lines,  as  follows,  "No  improvement  is  to  be  expected,  as  a 
general  thing,  from  exercise  of  the  interni;  overexertion, 
that  is  apt  to  occur,  may  result,  on  the  contrary,  in  a  serious 
impairment  of  their  power;"  Fuchs,  not  a  line;  Berry,  not 
a  line;  Meyer,  ten  lines;  Landolt,  not  a  line;  Wells,  one 
paragraph  of  ten  lines;  Schweigger,  not  a  line;  Nettleship, 
not  a  line;  Juler,  not  one  word;   Carter,  not  a  line. 

Those  of  the  twelve  authors  above  named  who  teach  any- 
thing on  the  subject  teach  the  same  thing.  This  teaching  is 
illustrated  by  the  following  quotation  from  DeSchweinitz: 
"  Thus,  to  exercise  the  interni  [in  exophoria]  a  prism  of  10 
degrees  is  placed  base  out  before  one  eye,  and  as  soon  as 
the    diplopia    produced   is   overcome,   5   degrees   more   are 

*  Published  in  the  Ophthalmic  Record,  May,  1893. 
(142) 


DEVELOPING   THE   OCULAR   MUSCLES.  I43 

added,  and  so  on  until  the  limit  of  adductive  power  is 
reached.  .  .  .  These  exercises  should  be  repeated 
every  day  for  ten  or  fifteen  minutes  at  a  time,  until  the  pa- 
tient has  acquired  the  power  to  overcome  readily  a  prism  of 
500."  He  recommends  the  same  character  of  exercise  for 
developing  the  externi,  beginning  with  a  30  prism  and  in- 
creasing to  8°. 

Noyes,  following  Dyer  who  wrote  on  this  subject  in  1865, 
says:  "  He  [the  patient]  takes  a  candle  flame  or  door  knob 
at  twenty  feet  for  his  object,  and  performs  the  efforts  of  ad- 
duction and  abduction  by  means  of  these  prisms.  He  be- 
gins, say,  with  adduction,  and  at  first  holds  the  prism  of  50, 
with  base  out,  before  one  eye;  then  substitutes  the  io°  ;  then 
before  the  other  eye  places  50,  making  a  total  of  150;  then, 
if  practicable,  substitutes  the  other  prism  of  io°  for  the  50; 
and  so  climbs  up  the  ladder  of  adduction  prisms  by  such 
steps  as  he  can  make.  If  the  interval  of  50  becomes  too 
great,  he  may  take  that  of  2^4°."  He  speaks  of  the  exer- 
cise of  the  externi  after  the  same  plan,  using  weaker  prisms 
with  their  bases  in.  He  directs  that  the  exercise  be  con- 
tinued ten  minutes  at  each  sitting,  and  that  it  be  repeated  not 
oftener  than  twice  a  day,  until,  in  the  case  of  the  interni,  a 
prism  of  42^°  can  be  readily  overcome,  and,  in  the  case  of 
the  externi,  a  prism  of  io°.  The  prism  of  maximum 
strength  having  been  reached,  its  use  should  be  continued, 
says  this  author,   once  daily  for  a  time.     Noyes  closes  by 


144  RHYTHMIC    EXERCISE    THE    PROPER    METHOD 

saying:  "A  decided  gain  in  comfort  and  use  of  the  eyes 
may  be  obtained  by  this  proceeding ;  and  if  this  result  is  not 
adequate,  the  true  state  of  the  muscular  relations  is  brought 
to  view." 

It  is  not  necessary  to  make  further  quotations  in  order  to> 
bring  clearly  into  view  the  character  of  the  exercise.  It  is 
the  object  of  this  paper  to  show  that  the  plan  is  unsound  in 
principle,  and  must  necessarily  be  unsuccessful  in  practice. 
Continuous  muscular  contraction,  augmented  at  short  inter- 
vals for  10  minutes,  or  for  even  5  minutes,  may  show  what  a 
muscle  is  capable  of  doing  in  an  emergency;  but  it  is  not 
calculated  to  build  up  or  develop  the  inherent  power  of  the 
muscle. 

In  a  modified  form  Dr.  Charles  E.  Michel,  of  St.  Louis, 
has  persistently  practiced  the  development  of  weak  internal 
recti  muscles  by  means  of  prisms,  since  1877.  The  prisms 
used  by  him  have  not  been  stronger  than  40,  nor  weaker  than 
i°.  Beginning  with  the  weaker  prism,  he  directs  the  patient 
to  exercise  frequently  (ten  to  fifteen  times)  during  the  day, 
each  period  of  exercise  to  last  only  four  or  five  minutes  for 
the  first  few  days;  later  they  are  to  be  worn  only  four  or 
five  times  daily,  increasing  the  time  of  exercise  by  two  to 
five  minutes  daily,  until  they  can  be  worn  comfortably  one 
hour.  When  the  patient,  looking  in  the  distance,  becomes 
able  to  wear  the  40  prism  one  hour  without  discomfiture,  he 
is  directed  to  commence  reading.     At  first  he  must  read  only 


OF    DEVELOPING    THE    OCULAR    MUSCLES.  I45 

from  three  to  five  minutes  at  a  time ;  but  later  he  increases, 
this  time  by  two  to  five  minutes  daily,  until  he  can  read  com- 
fortably one  hour,  four  times  a  day.  Whenever  this  can  be 
done,  the  patient  is  directed  to  continue  for  several  months 
the  reading  exercise  practice  for  half  to  one  hour,  two  or 
three  times  a  day.  To  suit  individual  cases,  modifications 
as  to  strength  of  prism  and  length  of  time  and  frequency  of 
exercise  must  be  made. 

Under  Dr.  Michel's  treatment,  fully  60  per  cent,  of  his 
patients  have  full  muscular  power  developed,  and  in  this 
way  are  enabled  to  use  their  eyes  with  comfort;  25  percent, 
have  greater  or  less  gain  in  comfort;  while  15  per  cent,  de- 
rive no  benefit  from  the  treatment.  As  a  preliminarvstep  to 
the  muscle  treatment,  the  Doctor  always  corrects  any  exist- 
ing refractive  errors,  and  has  the  patient  wear  these  lenses 
behind  the  exercise  prisms. 

Dr.  Michel's  method  of  developing  ocular  muscles  is 
given  for  the  reason  that  it  differs  essentially  from  that  set 
forth  in  the  books,  and  for  the  additional  reason  that  a 
high  percentage  of  cures  results  from  his  method.  The 
Doctor's  success  has  been  due  to  the  fact  that  his  weak 
prisms  used  made  but  little  demand  on  the  weak  muscles, 
thus  making  it  possible  for  the  continuous  contraction  to  be 
borne  and  the  muscle  strengthened. 

In  contrast  with  Dr.  Michel's  practice,  the  method  of  Dr. 

George  T.  Stevens,  of  New  York,  is  here  given  in  his  own 
10 


I46  RHYTHMIC    EXERCISE    THE    PROPER    METHOD 

words:  "Adduction  may  be  greatly  improved  by  gymnastic 
exercises  of  the  interni,  by  means  of  prisms.  In  these  ex- 
ercises, the  eyes  are  required  to  unite  images  in  overcoming 
gradually  increasing  obstacles.  A  prism  of  a  few  degrees, 
perhaps  io°,  is  placed,  base  out,  before  one  of  the  eyes,  while 
gazing  at  a  lighted  candle  at  twenty  feet  distance,  when  an 
effort  is  at  once  made  to  prevent  diplopia.  As  soon  as  the 
images  are  blended,  another  prism,  of  perhaps  less  degree, 
is  placed  in  the  same  manner.  The  images  being  united,  a 
stronger  prism  takes  the  place  of  one  of  those  already  in 
place,  or  one  is  added  to  those  already  in  position.  Thus, 
little  by  little,  the  eyes  are  required  to  overcome  prisms  until 
the  images  can  no  longer  be  united.  Then  all  the  glasses 
are  removed,  and  the  process  is  repeated;  with  each  repeti- 
tion something  may  be  gained.  The  exercise  should  not  be 
continued,  at  a  single  sitting,  more  than  five  or  six  minutes; 
and  only  a  single  sitting  daily  is  desirable.  By  this  means 
the  adducting  power  can,  in  most  cases,  be  raised  after  a 
few  exercises  to  the  desired  point. 

"  The  effect  of  such  exercise  upon  the  eyes  is  very  often 
extremely  salutary.  With  greater  freedom  of  muscular  ac- 
tion comes  a  sense  of  relief  from  nervous  strain,  which  is 
often  of  a  most  gratifying  character.  Such  an  exercise  is 
in  no  way  related  to  the  practice  sometimes  adopted,  and 
which  should  be  condemned,  of  requiring  the  patient  to 
gaze  for  a  long  time  at  a  near  object." 


OF    DEVELOPING    THE    OCULAR    MUSCLES.  I47 

The  virtue  of  Dr.  Michel's  method  lies  in  the  fact  that, 
though  he  taxes  the  muscles  for  a  long  while,  gradually 
reaching  the  maximum  of  time,  he  taxes  them  but  slightly, 
using  only  weak  prisms;  while  the  virtue  of  Dr.  Stevens's 
method  lies  in  the  fact  that,  while  he  taxes  the  muscles  se- 
verely, using  the  strongest  prisms  possible,  reaching  the 
maximum  strength  by  degrees,  he  does  not  continue  the  ex- 
ercise very  long  and  does  not  repeat  the  sitting  again  the 
same  day.  And,  too,  he  almost  strikes  the  right  principle 
in  his  method  of  intermitting  the  exercise. 

In  contrast  with  both  of  these  methods,  and  with  the 
method  laid  down  in  the  books,  the  method  of 

Rhythmic   Exercise 
wrill  now  be  given,    the   author  feeling  confident  that  it  is 
founded  on  sound  principles  and  that  it  can,  therefore,  be 
carried  out  successfully  in  practice. 

Contraction  and  relaxation,  alternating  in  short  and  rhyth- 
mic order,  and  continued  short  of  fatigue,  is  the  kind  of  ex- 
ercise that  develops  a  muscle  in  any  part  of  the  body.  It  is 
the  alternate  contraction  and  relaxation  that  develops  the 
muscles  of  the  arm  of  the  blacksmith.  If  the  forearm  should 
be  flexed  on  the  arm  and  held  in  that  position  ten  minutes, 
no  one  would  suppose  that  the  muscles  concerned  could  be 
developed  thereby.  There  would  be  greater  reason  for  be- 
lieving that  such  action  would  enfeeble  the  muscles.     This 


I48  RHYTHMIC    EXERCISE    THE    PROPER    METHOD 

is  precisely  the  kind  of  contraction  effected  by  prisms  in 
the  old  method  of  exercising  the  recti  muscles.  There  can 
be  no  wonder  that  better  results  have  not  followed,  and  that 
the  practice  has  been  abandoned  by  almost  all  oculists. 

This  paper  would  be  of  little  worth  if  it  condemned  the 
old  practice  as  bad  without  setting  forth  a  new  line  of  prac- 
tice, based  on  sound  principles,  and  one  that  must  be  suc- 
cessful, in  suitable  cases. 

While  rhythmic  contraction  and  relaxation,  regulated  as 
to  intensity  and  time,  will  develop  any  one  of  the  recti  mus- 
cles, as  is  developed  the  biceps  of  the  blacksmith,  the  writer 
would  not  be  understood  as  believing  that  one  of  these  mus- 
cles can  be  developed  out  of  a  low  state  of  weakness  into  a 
high  state  of  strength.  There  are  case  of  exophoria  that 
will  remain  exophoric  still  in  spite  of  long-continued 
rhythmic  and  graduated  exercise;  and  these  cases,  to  be 
cured  at  all,  must  be  cured  either  by  partial  tenotomies 
alone,  or  by  these  supplemented  with  rhythmic  exercise. 
The  same  may  be  said  of  esophoria  and  hyperphoria.  Only 
low  degrees  (not  more  than  6°)  of  lateral  heterophoria  can, 
by  rhythmic  exercise  alone,  be  converted  into  orthophoria; 
the  highest  degrees  can  be  corrected  by  partial  tenotomies, 
shortenings,  and  exercise  combined.  While,  in  suitable 
cases,  the  aim  of  partial  tenotomies  and  shortenings  should 
be  to  approach  orthophoria,  yet  the  greatest  care  should  be 
exercised  not  to  go  beyond  the  "  balance  "  line.     The  safest 


OF    DEVELOPING    THE    OCULAR    MUSCLES.  1 49 

thing  is  to  leave,  for  correction  by  exercise,  some  of  the 
original  condition. 

In  attempts  to  develop  the  ocular  muscles  after  the 
rhythmic  contraction  and  relaxation  method,  it  must  not  be 
forgotten  that  the  extrinsic  muscles  of  the  eye  are  under  the 
control  of  the  guiding  sensation  in  the  retina,  through  the 
will. 

Any  one  of  the   recti  and  either  of  the  obliques  weaker 

than  its  opposing  muscle,   the   difference  in  corresponding 

strength  not  being  too  great,  may  be  developed  by  rhythmic 

exercise  into  a  state  that  will  enable  it  to  work  harmoniously 

with  its  fellow. 

Exophoria. 

Exophoria  may  be  taken  first  for  study.  The  quantity 
should  not  be  more  that  6°.  The  internal  recti  are  the  mus- 
cles wanting  in  strength.  There  are  two  plans  of  exercise, 
rhythmic  in  their  nature,  by  either  one  of  which,  or  by  both 
combined,  these  muscles  can  be  strengthened: 

i.  The  wax  taper  method ; 

2.  The  method  by  prisms,  bases  out. 

The  exercise  with  the  taper  (small  wax  candle)  must  be 
conducted  as  follows:  The  patient  is  directed  to  light  the 
taper  and  hold  it  at  arm's  length  from,  and  on  a  plane  with, 
the  eyes,  immediately  in  front  of  the  face.  Fixing  his  vis- 
ion on  the  flame,  he  continues  to  look  at  it  while  he  brings 
it  slowly  to  within  five  inches  of  his  eyes,  holding  it  there 


150  RHYTHMIC    EXERCISE    THE    PROPER    METHOD 

about  two  seconds.  He  then  closes  his  eyes  for  a  moment, 
and  on  opening  them  he  fixes  his  vision  on  some  object,  pref- 
erably the  flame  of  a  candle  or  lamp,  twenty  feet  or  more 
distant.  The  same  procedure  is  gone  through  with  a  second 
time,  and  so  on  for  six  to  ten  times  at  the  one  sitting;.  The 
sittings  may  be  repeated  two  or  more  times  daily  for  weeks 
or  months.  The  best  time  for  this  exercise  is  early  in  the 
morning,  while  the  muscles  are  fresh  from  sleep.  In  many 
cases  the  morning  sitting  will  be  sufficient  for  the  day.  This 
is  especially  so  if  the  exophoria  is  low  in  degree.  Reading 
or  other  near  work  should  not  be  done  within  the  hour  after 
exercise. 

In  this  taper  exercise  no  one  can  doubt  that  the  guiding 
sensation  compels  the  internal  recti  to  contract  as  the  light 
advances,  the  maximum  of  contraction  being  reached  when 
the  taper  is  five  inches  from  the  eyes.  On  closing  the  eyes 
partial  relaxation  of  the  interni  occurs  (keeping  the  eyes 
closed  long  enough,  the  relaxation  would  become  complete). 
The  moment  the  eyes  are  opened  and  the  vision  is  fixed  on  a 
distant  object,  in  quick  response  to  the  guiding  sensation, 
the  relaxation  becomes  complete.  Thus  is  brought  about 
contraction  and  relaxation,  which  should  be  discontinued  short 
of  fatigue.  That  this  rhythmic  exercise,  properly  regulated 
as  to  frequency  and  to  force,  will  develop  the  internal  recti 
is  susceptible  of  demonstration  on  the  part  of  any  one  who 
wishes  to  know  the  truth. 


OF    DEVELOPING    THE    OCULAR    MUSCLES.  151 

The  second  method  for  developing  the  interni  is  by  means 
of  prisms,  bases  out.  The  prisms  to  be  used  may  be  from 
i°  to  8°,  and  one  should  be  placed  before  each  eye.  The 
treatment  should  be  commenced  with  the  weaker  prisms; 
and  as  development  of  the  muscles  advances,  the  stronger 
should  be  brought  into  use.  The  object  looked  at  should  be 
a  candle,  lamp,  or  gas  jet,  fifteen  to  twenty  feet  distant. 
The  prisms  before  the  eyes,  the  image  in  each  of  the  two 
eyes  is  displaced  out,  and  the  guiding  sensation  calls  quickly 
into  action  the  interni.  After  five  seconds  the  interni  must 
be  allowed  to  relax  for  the  same  length  of  time  (five  sec- 
onds), which  is  readily  effected  by  lifting  the  prisms  up  and 
allowing  the  light  to  enter  the  eyes  uninfluenced.  The 
guiding  sensation  at  once  causes  the  relaxation  to  take  place, 
so  that  the  yellow  spots  may  receive  the  images.  At  the  end 
of  this  five  seconds,  the  prisms  are  again  dropped  before  the 
eyes,  and  the  interni  again  contract.  Then  a  second  time 
the  relaxation  is  effected  by  lifting  the  prisms ;  _  and  so  on 
throughout  every  sitting,  which  should  last  from  two  to  ten 
minutes,  but  always  discontinued  short  of  fatigue.  The  sit- 
tings should  be  repeated  two  to  five  times  a  day.  While  it 
will  take  weeks  if  not  months  to  establish  orthophoria,  nev- 
ertheless this  end  can  be  attained,  in  suitable  cases,  by  this 
method.  It  may  be  better  in  most  cases  to  resort  to  the  two 
methods  of  development,  the  taper  and  the  prisms,  each 
day,  but  not  at  the  same  sitting. 


152  RHYTHMIC    EXERCISE    THE    PROPER    METHOD 

In  resorting  to  the  prism  exercise,  it  would  be  more  con- 
venient to  close  the  eyes,  for  the  purpose  of  getting  relaxa- 
tion, than  to  lift  the  prisms.  When  the  eyes  are  closed  the 
relaxation  is  slow  to  take  place,  and  is  rarely  complete  at 
the  end  of  sixty  seconds;  whereas,  when  the  prisms  are 
raised,  the  guiding  sensation  effects  at  once  complete  relax- 
ation, which  continues  until  the  prisms  are  again  placed  be- 
fore the  eyes.  The  rhythmic  nature  of  the  exercise  is  more 
perfect  in  the  latter  than  in  the  former,  and  results  are  bet- 
ter necessarily. 

Esophoria. 

In  this  condition  the  muscles  to  be  built  up  are  the  ex- 
ternal recti.  There  is  but  one  method  for  doing  this,  and 
that  is  by  means  of  prisms.  These  should  be  from  ]/20  to  30, 
certainly  not  more  than  40,  and  their  bases  must  be  placed 
in.  Beginning  with  the  weaker  prisms,  the  patient  should 
look  at  the  candle  twenty  feet  distant  for  five  seconds,  dur- 
ing which  time  the  guiding  sensation  has  caused  the  externi 
to  undergo  contraction;  and  then  the  prisms  should" be  held 
up  for  five  seconds  to  allow  relaxation  to  take  place.  These 
steps  should  be  thus  regularly  repeated  throughout  each  sit- 
ting of  two  to  ten  minutes,  the  sittings  themselves  being  re- 
peated from  two  to  five  times  daily,  as  in  treatment  of  exo- 
phoria.     In  suitable  cases  orthophoria  can  be  brought  about. 

Hyperphoria. 

Hyperphoria  and  cataphoria,  like  esophoria,  are  suscepti- 


OF    DEVELOPING    THE    OCULAR    MUSCLES.  153 

ble  only  to  exercise  by  means  of  prisms.  Given  a  case 
of  left  hyperphoria  (right  cataphoria)  of  not  more  than  1*4°, 
there  is  a  possibility  of  developing  vertical  orthophoria  by 
means  of  rhythmic  exercise.  The  muscle  on  the  left  side  to 
be  developed  is  the  inferior  rectus,  and  that  on  the  right  side 
the  superior  rectus.  The  prisms  used  should  vary  from  y£* 
to  2° — most  cases  will  not  require  a  stronger  than  a  i° 
prism.  The  base  of  the  left  prism  must  be  up  and  that 
of  the  right  down.  As  in  exophoria  and  esophoria,  the 
patient  should  exercise  from  two  to  ten  minutes  at  a  time, 
and  two  to  five  times  a  day.  The  object  looked  at  should 
be  twenty  feet  distant,  and  it  should  be  seen  through  the 
prisms  five  seconds,  then  without  the  prisms  five  seconds, 
and  so  on  throughout  each  sitting.  Thus  contraction  and 
relaxation  of  the  weak  left  inferior  rectus  and  weak  rio-ht 
superior  rectus  are  effected  in  rhythmic  order.  If  the  hy- 
perphoria is  on  the  right  side  (left  cataphoria),  the  base  of 
the  right  prism  must  be  up  and  that  of  the  left  down.  In 
every  form  of  heterophoria  the  angle  of  the  prism  must 
point  in  the  direction  of  the  muscle  to  be  developed  by  it. 

Occasionally  cases  present  themselves  in  which  there  is  a 
general  weakness  of  the  recti  muscles,  and  especially  of  the 
external  and  internal  recti,  unaccompanied  by  general  phys- 
ical weakness.  Such  cases  generally  manifest  esophoria  for 
distance  and  exophoria  in  the  near,  neither  muscle  being 
able    to    overcome    a    prism    of    anything    like    the    usual 


154  RHYTHMIC    EXERCISE    THE    PROPER    METHOD 

strength.  To  operate  on.  such  a  case  would  be  improper, 
since  relief  of  the  exophoria  in  the  near  would  be  attended 
by  a  corresponding  increase  of  the  esophoria  for  distance, 
and  vice  versa.  In  such  cases  the  interni  should  be  brought 
under  the  influence  of  the  rhythmic  exercise,  as  already  set 
forth  in  our  study  of  exophoria,  at  one  time  of  the  day;  and, 
at  some  other  time  of  the  day,  like  attention  should  be  paid 
to  the  external  recti,  as  in  simple  esophoria.  In  these  cases 
strychnia  and  electricity  could  be  used  with  some  promise  of 
aiding  the  exercise  treatment.  Such  patients  should  be  al- 
lowed to  undertake  but  little  near  work,  until  the  exercise 
treatment  by  means  of  prisms  has  become  well  advanced. 
In  these  cases  the  wax  taper  treatment  of  the  internal  recti 
is  not  applicable  until  late  in  the  course.  These  cases  are 
far  more  stubborn  than  cases  of  simple  exophoria  and  sim- 
ple esophoria;  and  yet  great  advantage  can  be  derived  from 
the  rhythmic  exercise  by  means  of  weak  prisms,  aided  by 
strychnia  and  electricity. 

In  cases  in  which  the  recti  muscles  are  weak,  because  of  a 
low  state  of  general  health,  no  treatment  should  be  thought 
of  except  that  intended  for  the  well-being  of  the  whole  sys- 
tem. Use  of  the  eyes  in  near  work  should  be  prohibited 
until  recovery  of  the  general  health  has  occurred. 

Cyclophoria. 

The  treatment  of  insufficiency  of  the  oblique  muscles,  as 
set  forth  in  No.  i  of  the  current  volume  of  the  Ophthalmic 


OF    DEVELOPING    THE    OCULAR    MUSCLES.  155 

Record,  is  by  means  of  cylindrical  lenses  (preferably  con- 
vex), so  placed  as  to  lead  the  guiding  sensation  to  demand 
contraction  on  the  part  of  the  weak  muscles.     The  -j-1.50 
D.  cylinder  is  the  most  useful,  but  a  weaker  one  may  be 
used  at  the  beginning.     One  should  be  placed  before  each 
eye ;  and  if  the  weak  muscles  are  the  superior  obliques,  their 
axes  must  be  placed  in  the  lower  temporal  quadrant,  at  first 
150  from  the  vertical,  when,  because  of  the  slight  retinal  dis- 
placement of  the  object  looked  at,  only  a  slight  demand  is 
made  on  the  muscles,  which  should  be  kept  up,  in  an  inter- 
mitting way,  for  five  minutes;   then  the  axes  should  be  re- 
volved to  300  from  the  vertical,  when,  because  of  a  greater 
displacement  of  the  images,  a  greater  demand  for  contrac- 
tion is  made  on  the  part  of  the  weak  obliques,  which  should 
be  kept  up  intermittingly  for  three  minutes;    now,  lastly,  the 
axes  of  the  cylinders  are  revolved  to  450  from  the  vertical, 
when  the  maximum  displacement  of  the  images  occurs,  and 
hence  the  maximum  demand  is  made  on  the  muscles,  which 
should  be    continued   intermittingly   for   two   minutes   only. 
As  in  the  exercise  of  the  recti  by  means  of  prisms,  the  best 
way  to  get    contraction   and    relaxation  alternately  and   in 
rhythmic  order  is  to  lower  and  raise  the  frames  containing 
the  prisms  every  five  seconds;  so,  to  get  rhythmic  contrac- 
tion and  relaxation  of  the  obliques  under  exercise,  it  is  best 
to  lower  and  raise  the  frames  containing  the  cylinders  every 
five  seconds  throughout  the  sitting.     It  is  unfortunate  for  the 


156  RHYTHMIC    EXERCISE    THE    PROPER    METHOD 

convenience  of  the  patient  that  the  relaxation  of  ocular  mus- 
cles does  not  quickly  follow  the  closing  of  the  eyes,  since  it 
would  be  much  easier  to  open  and  close  the  eyes  every  five 
seconds  than  to  lower  and  raise  the  frames  at  the  same  in- 
terval. The  oblique  muscles  relax  much  more  readily  than 
the  recti  on  closing  the  eyes,  but  even  these  do  not  com- 
pletely relax  in  the  short  time  of  five  seconds. 

In  most  cases  of  insufficiency  of  the  obliques,  exercising 
by  means  of  cylinders  once  a  day  is  usually  sufficient.  The 
best  time  for  this  exercise  is  before  breakfast;  the  object 
looked  at  should  be  a  wide  lamp  blaze  fifteen  to  twenty  feet 
distant.  The  cylinders  should  be  properly  centered.  What 
prisms  are  to  the  recti,  cylinders  are  to  the  obliques.  In 
either  case,  the  lenses  correcting  refractive  errors  should  be 
worn  during  the  exercise,  in  order  that  the  best  results  may 
follow.  The  only  exception  to  this  rule  is  the  wax  taper  ex- 
ercise of  the  internal  recti,  when  no  lenses  should  be  worn. 

The  expression  "  in  suitable  cases  "  has  occurred  fre- 
quently in  this  paper,  and  has  been  properly  used.  Its  use 
implies  that  there  are  cases  of  heterophoria  not  suited  to 
the  exercise  treatment.  Such  cases  are  numerous,  and  how 
to  manage  them  is  a  most  interesting  question.  The  higher 
the  degree  of  heterophoria,  shown  after  a  focal  error  has 
been  fully  corrected,  the  greater  the  necessity  for  operative 
interference,  and  the  more  extensive  must  be  the  operations. 
Given  a  case  of  exophoria  of  io°  in  the  near  and  6°  at  a  dis- 


OF    DEVELOPING    THE    OCULAR    MUSCLES.  157 

tance,  we  should  attempt  to  correct  the  6°  by  operations,  ef- 
fecting, as  nearly  as  possible,  half  this  correction  by  a  par- 
tial tenotomy  of  one  external  rectus,  and  the  balance  by  a 
partial  tenotomy  of  the  other,  from  three  to  six  weeks  later. 
To  do  more  than  this  by  means  of  the  operations  would  be 
to  develop  some  esophoria  for  distance,  a  thing  not  desir- 
able ;  while  to  do  less  would  be  to  run  the  risk  of  leaving 
so  much  exophoria  that  the  rhythmic  exercise,  by  means  of 
the  wax  candle  or  by  prisms,  one  or  both,  could  not  bring 
about  orthophoria. 

In  still  another  case  the  exophoria  might  be  so  great  that, 
after  a  partial  tenotomy  had  been  done  on  each  external  rec- 
tus, there  remain  a  few  degrees  of  exophoria  for  distance, 
so  much  that  there  can  be  no  hope  of  curing  by  exercise. 
In  such  a  case,  instead  of  trying  to  effect  more  by  repeating 
the  operation  on  either  one  or  both  of  the  externi,  one  or 
both  of  the  interni  should  be  shortened.  As  in  partial  te- 
notomies, so  in  shortenings,  it  is  better  to  divide  the  opera- 
tion between  the  two  corresponding  muscles,  for  reasons 
long  since  given  by  Stevens.  Having  corrected  all  the  exo- 
phoria for  distance,  falling  only  a  little  short  or  going  only 
a  little  beyond,  that  remaining  in  the  near  may  be  relieved 
by  the  methods  of  exercise  already  set  forth ;  but  in  no  case 
should  the  exercise  be  commenced  within  six  weeks  after 
the  last  operation. 

In    relieving    esophoria    by    operations    and   exercise    the 


158  RHYTHMIC    EXERCISE    THE    PROPER    METHOD 

principles  laid  down  for  exophoria  hold  good,  the  operations 
on  the  muscles  being  reversed;  and,  too,  the  esophoriatobe 
corrected  is  that  determined  by  the  near  test,  leaving  the 
difference  shown  between  the  near  and  the  far  tests  to  be 
corrected  by  the  rhythmic  exercise  of  the  externi. 

In  left  hyperphoria  of  not  less  than  ij4°  nor  more  than 
30,  this  being  as  a  rule  the  same  for  distance  and  in  the 
near,  some  of  it  should  be  relieved  by  partial  tenotomy  of  the 
left  superior  rectus  and  the  balance  cured  by  exercising  the 
left  inferior  and  the  right  superior  recti;  but  if  there  is  more 
than  30  of  the  vertical  error,  the  operative  effect  should  be 
divided  between  the  superior  of  the  left  and  inferior  of  the 
right,  allowing  an  interval  of  not  less  than  four  weeks  be- 
tween the  operations.  Rather  than  over-correct,  leave  some 
of  the  original  error  for  correction  by  the  exercise. 

As  to  cyclophoria  nothing  is  applicable  except  the  exer- 
cise by  means  of  cylinders. 

Whenever  more  than  one  of  these  muscular  errors  exist  at 
the  same  time,  all  should  be  corrected  by  either  exercise  or 
operation,  or  both. 


I  have  had  made,  for  the  convenience  of  my  patients, 
three  sets  of  exercise  prisms ;  an  exophoric  set,  an  eso- 
phoric  set,  and  a  hyperphoric  set.  The  box  for  each  set  is 
6y2  inches  long,  one  inch  wide,  and  i1/^,  inches  deep.  On 
one  side,  from  end  to  end,  there  are  five  compartments  of 


OF    DEVELOPING    THE    OCULAR    MUSCLES.  159 

equal  size  for  holding  the  five  loose  prisms.  The  remainder 
of  the  space  in  the  box  is  for  the  frames,  which  should  be  of 
German  silver,  with  No.  i  oval  rims  and  a  pupillary  dis- 
tance of  2^  inches.  The  grooves  of  the  rims  should  be 
deep  enough  to  hold  readily  the  prisms;  and  the  screws  for 
confining  the  prisms  should  have  a  neck  ^  °f  an  inch  long, 
terminating  in  a  milled  head,  so  that  the  patient  can  readily 
remove  one  prism  and  put  another  in  its  place. 

The  "  exophoric  case"  contains,  in  addition  to  the 
frames,  one  each  of  the  following  prisms:  i°,  2°,  30,  40,  50, 
6°,  and  8°.  These  prisms  are  so  cut  that  their  bases  can 
be  placed  out,  as  they  must  be  in  order  to  exercise  the 
weak  internal  recti. 

The  "  esophoric  case"  contains  the  following  seven 
prisms:  %° ,  i°,  i^°,  2°,  2%°,  30,  and  40.  These  must 
be  so  cut  that  their  bases  may  be  placed  in,  as  they  must  be 
in  order  to  exercise  the  weak  external  recti. 

The  "  hyperphoric  case"  should  contain  five  prisms,  as 
follows:  %°,  y2°,  i°,  i}4°,  and  20.  These  must  be  so  cut 
that  their  bases  may  be  placed  up  and  down. 

The  manner  of  placing  these  prisms,  in  an  individual 
case,  has  already  been  set  forth,  as  has  also  the  method  of 
exercise.  As  to  method  of  exercise,  a  little  more  may  be 
said.  The  prisms  are  not  in  pairs,  because  of  the  additional 
cost  to  the  patient  such  an  arrangement  would  involve. 
Taking  an  exophoric  patient,  I  would  place  in  the  frames 


l6o  RHYTHMIC    EXERCISE    THE    PROPER    METHOD 

the  i°  prism  for  one  eye  and  the  2°  prism  for  the  other 
eye,  bases  out.  I  would  have  the  patient  exercise  for  five 
days,  and  then  transfer  the  two  prisms  and  exercise  for  five 
more  days.  At  the  end  of  this  period  I  would  have  the  i° 
prism  removed  and  the  30  prism  put  in  its  place,  directing 
the  patient  to  exercise  with  the  new  combination  for  five 
days,  and  then  transfer  the  prisms  and  exercise  through  an- 
other period  of  five  days.  I  would  now  remove  the  2a 
prism  and  in  its  place  put  the  40  prism,  directing  the  patient 
to  exercise  with  the  new  combination  for  five  days,  at  the 
end  of  which  time  I  would  have  him  transfer  the  prisms  and 
exercise  five  days  more.  Now  the  30  prism  should  be  sub- 
stituted by  the  50  prism.  This  new  combination  should  be 
used  for  five  days,  when  a  transfer  of  the  40  and  50  prisms 
should  be  made,  to  be  followed  by  another  five  days  of  ex- 
ercise. Now  the  40  prism  should  be  substituted  by  the  6° 
prism,  and  the  exercise  should  be  repeated  as  with  the  other 
combinations.  At  the  end  of  this  ten  days  the  50  prism 
should  be  removed  and  the  8°  prism  put  in  its  place.  From 
now  on  to  the  end  of  the  treatment  the  6°  prism  and  the  8° 
prism  should  be  transferred  every  five  days.  Whenever 
transfers  are  made  or  new  prisms  substituted,  their  bases 
must  always  be  placed  out,  in  the  treatment  of  exophoria. 
Following  the  above  plan,  the  exercise  is  continued  for  fifty 
days  before  reaching  the  strongest  prism.  With  the  stron- 
gest pair  the  exercise  should  be  continued  until  the  tests  show 


OF    DEVELOPING    THE    OCULAR    MUSCLES.  l6l 

that  there  is  muscular  balance,  which  may  be  in  a  few  weeks 
or  a  few  months.  Because  of  the  mild  nature  of  this  meth- 
od of  exercise,  I  am  convinced  that,  for  most  persons,  it  is 
better  than  the  method  by  means  of  the  wax  taper. 

In  using  the  esophoric  set  for  the  cure  of  esophoria,  be- 
ginning with  the  weakest  prisms,  the  strongest  are  reached 
in  the  same  methodical  way  as  in  using  the  exophoric  set, 
the  only  difference  being  that  the  bases  of  the  prisms  are 
placed  in  instead  of  out. 

In  using  the  hyperphoric  set  the  same  general  plan  as  to 
time  of  exercise,  the  transferring  and  replacing  of  prisms, 
beginning  with  the  weakest  and  finally  reaching  the  stron- 
gest, should  be  observed.  Always  the  base  of  the  prism 
must  be  up  for  the  hyperphoric  eye  and  down  for  the  cata- 
phoric eye.  Two  or  three  sittings  a  day  and  ten  minutes  at 
each  sitting  is  the  correct  practice. 

The  strength  of  every  prism  should  be  distinctly  marked 
on  its  base,  so  that  the  necessary  changes  may  be  easily  and 
accurately  made  by  the  patient. 

To  make  the  rhythmic  exercise  as  easy  as  possible,  I  have 

had  made  an  instrument  for  raising  and  lowering  the  frames. 

It  is  simple  and  can  be  readily  made   as  follows:   Take  a 

piece  of  steel  wire  one-eighth  of  an   inch  in  diameter  and 

eight  inches  long;   file  it  on  two  sides  for  a  distance  of  one 

inch,  until  it  is  sufficiently  thin  to  be  bent  somewhat  in  the 

shape  of  the  neck  of  a  goose,  and  fix  the  other  end  in   a 
11 


l62  DEVELOPING    THE    OCULAR    MUSCLES. 

wooden  handle  about  four  inches  long.  The  goose-neck 
extremity  is  made  to  grasp  the  shank  of  the  frames  on  ei- 
ther side,  between  the  rim  and  the  temple  piece,  which  it 
should  fit  sufficiently  tight  to 'hold  the  frames  firmly.  With 
handle  in  hand,  the  frames  can  be  raised  and  lowered  every 
five  seconds  without  inducing  fatigue  of  the  arm. 

Further  experience,  coupled  with  close  observation,  in  de- 
veloping weak  internal  recti  muscles  leads  me  to  the  con- 
clusion that,  for  children  who  are  exophoric,  and  in  whom 
the  ciliary  muscle  is  strong,  the  wax  taper  exercise  is  the 
better  of  the  two  plans.  The  short  time  devoted  to  the  ta- 
per exercise  makes  it  well  suited  to  children  who  would 
soon  get  impatient  under  the  ten  minutes  rule  with  the 
prisms.  For  adults,  especially  those  approaching  middle 
life  or  beyond  it,  in  whom  the  muscle  of  accommodation  is 
not  so  strong  as  in  children,  the  prism  exercise  is  better. 
Understanding  the  reasons  for  the  exercise,  the  adult  will- 
ingly comes  under  the  ten  minutes  rule. 


Since  the  publication  of  this  chapter  on  "  Rhythmic  Ex- 
ercise the  Proper  Method  of  Developing  the  Ocular  Mus- 
cles," I  have  adopted  a  modification  of  the  method,  as  to 
exophoria,  set  forth  therein,  but  resort  to  it  only  after  the 
original  method  ("fixing"  only  a  lighted  candle  or  gas  jet 
at  fifteen  to  twenty  feet)  has  been  practiced  for  from  two  to 
four  or  more  weeks.     Briefly  it  is  this:   The  patient  must 


DEVELOPING   THE   OCULAR   MUSCLES.  163 

be  seated  from  fifteen  to  twenty  feet  from  the  lighted  candle 
or  gas  jet,  and  must  have  in  one  hand  a  white  card  on 
which  is  a  cross  or  a  dot.  With  the  prisms  on,  the  patient 
must  look  first  at  the  distant  blaze  for  about  two  seconds; 
then  at  the  dot  on  the  card,  held  at  the  reading  distance,  for 
about  two  seconds;  then  at  the  blaze  again  for  two  seconds, 
when  the  frames  containing  the  prisms  should  be  elevated 
for  five  seconds,  during  which  time  the  vision  is  kept  fixed 
on  the  blaze.  Now  lowering  the  frames,  the  patient  con- 
tinues to  look  at  the  blaze  through  the  prisms  for  two  sec- 
onds ;  then  at  the  dot  on  the  card  as  before  for  two  seconds, 
and  again  at  the  blaze  for  two  seconds,  when  the  frames  are 
again  elevated  for  five  seconds,  the  patient  continuing  to 
look  at  the  blaze,  thus  allowing  the  internal  recti  to  fully 
relax.  The  procedure  is  again  repeated,  and  so  on  to  the 
end  of  the  sitting — ten  minutes.  This  modification  is  a  little 
complex,  but  patients  can  be  readily  taught  how  to  resort  to 
it.  I  am  convinced  that  it  will  add  greatly  to  the  rapidity  of 
the  cure. 

As  the  treatment  advances,  the  prisms  should  be  shifted 
and  replaced  as  already  set  forth  in  this  chapter. 


CHAPTER  VIII. 

STHENIC  AND  ASTHENIC  ORTHOPHORIA,  AND 
STHENIC  AND  ASTHENIC  HETEROPHORIA. 

There  is  such  a  condition  as  lateral  orthophoria,  in  which 
neither  the  interni  nor  externi  are  sufficiently  strong.  There 
is  also  such  a  condition  as  vertical  orthophoria,  in  which  both 
the  superior  and  inferior  recti  are  weak.  Of  the  former  we 
had  something  to  say  at  the  last  meeting  of  the  American 
Medical  Association  (Baltimore,  1895);  we  have  known  of 
the  existence  of  the  latter  since  November,  1895.  Since 
there  are  two  kinds  of  orthophoria,  it  seems  necessary  to 
have  terms  for  distinguishing  them.  Sthenic  orthophoria 
would  aptly  describe  the  form  in  which  the  muscle  balance 
is  in  strength;  while  asthenic  orthophoria  would  apply  to 
that  form  in  which  the  muscle  balance  is  in  weakness.  It 
is  evident  that  only  asthenic  orthophoria  should  receive  any 
consideration,  from  a  therapeutic  standpoint. 

As  there  are  two  kinds  of  orthophoria,  there  are  also  two 
forms  of  heterophoria,  the  sthenic  and  the  asthenic,  the  one 
being  easily  distinguishable  from  the  other,  and  each  requir- 
ing its  own  proper  therapeutic  procedure. 
Sthenic  Orthophoria. 

This  condition  is  not  often  encountered,  though  it  occurs 
(164) 


AND    STHENIC   AND   ASTHENIC    HETEROPHORIA.  165 

more  frequently  than  the  asthenic  form.  In  lateral  ortho- 
phoria of  the  sthenic  type  the  externi  are  found  to  balance 
the  interni  in  both  the  far  and  the  near  tests,  and  abduction  is 
8°  or  more.  These  conditions  found,  there  is  no  need  for 
testing  the  adduction,  nor  does  there  exist  an  indication  for 
the  application  of    any  therapeutic  law  to  the  lateral  ocular 

muscles. 

Sthenic  orthophoria  as  applied  to  the  vertically  acting 
muscles  is  determined  by  the  balancing  of  these  muscles  in 
the  distant  test,  associated  with  a  deorsumduction  of  30  or 
more.  This  condition,  when  found,  cannot  be  made  better, 
for  it  is  already  perfect. 

Asthenic  Orthophoria, 
as  applied  to  the  lateral  muscles,  manifests  itself  by  a  low 
abduction  (less  than  8°)  associated  with  a  balancing  of  these 
muscles  in  both  the  far  and  the  near  tests.  Finding  the  exter- 
nus  weak,  although  capable  of  balancing  its  opposing  mus- 
cle, it  at  once  appears  that  the  internus,  too,  must  be  weak. 
The  lower  the  abduction  in  this  condition  the  worse  is  the 
case.  We  have  at  our  command  two  methods  of  treatment, 
either  one  of  which,  or  both  combined,  will  bring  great  relief 
to  the  patient.  The  first  method  consists  of  prismatic  exercise 
of  both  the  interni  and  the  externi.  The  most  convenient 
arrangement  of  such  prisms  is  that  suggested  by  Dr.  George 
H.  Price  about  two  years  ago — viz.,  prisms  put  in  ordinary 
spectacle  frames   like  Franklin  divided   lenses,  the   upper 


l66  STHENIC   AND   ASTHENIC   ORTHOPHORIA, 

prisms  with  bases  in,  the  lower  with  bases  out.  Since  the 
indication,  in  lateral  asthenic  orthophoria,  is  to  add  equally 
to  the  tonicity  of  the  externi  and  the  interni,  the  prisms  in 
the  upper  part  of  the  rim  should  be  of  the  same  strength  as 
those  in  the  lower.  The  objects  to  be  looked  at  during  the 
period  of  exercise  should  be  a  candle,  lamp  or  gas  jet 
placed  twenty  feet  from  the  patient,  and  a  card  with  a  dot 
or  cross  mark  on  it  to  be  held  in  the  hand.  Viewing  the 
light  through  the  upper  prisms,  the  externi  are  made  to  con- 
tract, so  as  to  effect  binocular  single  vision ;  while  looking  at 
the  mark  on  the  card  through  the  lower  prisms  calls  into  ac- 
tion the  interni.  The  light  and  the  dot  are  fixed  alternately 
every  five  seconds,  and  thus  is  excited  rhythmic  contraction 
and  relaxation  of  the  lateral  muscles.  The  exercise  should 
be  continued  five  or  ten  minutes,  and  should  be  repeated 
twice  or  oftener  in  the  twenty-four  hours.  The  prisms  used 
need  never  be  stronger  than  40,  and,  as  in  the  heterophoric 
condition,  it  would  be  better  to  commence  with  weaker 
prisms. 

The  other  method  of  exercising  these  muscles  is  the  syn- 
chronous moving  of  the  eyes  in  the  horizontal  plane  to  the 
right  and  left  alternately,  fixing  for  only  a  moment  some  ob- 
ject previously  placed  on  the  wall  for  the  purpose.  Since 
this  will  usually  be  done  in  a  room,  it  might  be  named  the 
"wall-to-wall"  exercise.  The  point  of  view  should  be 
changed  from  side  to  side  every  few  seconds,  and  the  ex- 


AND   STHENIC   AND   ASTHENIC    HETEROPHORIA.  l6j 

ercise  should  be  continued  five  to  ten  minutes,  but  should 
always  be  stopped  short  of  fatigue.  Two  ways  of  modify- 
ing the  treatment  in  the  beginning,  so  as  not  to  excite  fatigue, 
would  naturally  suggest  themselves:  the  one  looking  far 
to  the  right  and  left  for  only  a  short  while ;  the  other  look- 
ing only  a  little  way  to  the  right  and  left  for  several  minutes. 
In  the  one,  the  time  should  be  increased  gradually;  in  the 
other,  the  arc  to  be  described  by  the  visual  axes  must  be 
extended  gradually  to  the  utmost  capacity  of  the  binocular 
sweep.  In  any  case,  either  method  alone  would  serve  to  add 
strength  equally  to  the  muscles  exercised ;  both  methods 
might  be  combined  in  any  case  with  profit,  the  patient  be- 
ing directed  to  resort  to  the  wall-to-wall  exercise  every 
morning  and  the  prismatic  exercise  in  the  evening.  As  the 
treatment  progresses,  the  abduction  should  be  tested  at  in- 
tervals of  a  few  weeks,  and  when  this  reaches  8°  there  is  no 
further  indication  for  treatment. 

Asthenic  Vertical  Orthophoria 
was  first  noticed  by  the  writer  in  November,  1895.  The 
first  patient  was  astigmatic,  and  had  slight  exophoria  in  the 
near,  with  abduction  of  8°.  There  was  no  hyperphoria.-. 
Her  focal  error  was  corrected  and  her  exophoria  in  the 
near  responded  readily  to  rhythmic  exercise.  Her  eyes  were 
still  incapable  of  comfortable  near  work,  for  which  there 
seemed  to  be  no  explanation.  A  statement  by  the  patient 
divulged  the   secret  of  her  trouble.     She  said  that  if   she 


l68  STHENIC   AND   ASTHENIC   ORTHOPHORIA, 

should  hold  a  book  or  paper  on  a  level  with  her  eyes  she 
could  read  with  a  fair  degree  of  comfort.  It  at  once  ap- 
peared that,  while  there  was  vertical  orthophoria,  there  was 
nevertheless  weakness  of  the  superior  and  inferior  recti  of 
both  eyes.  The  strength  test  confirmed  the  suspicion,  for 
her  sursumduction  and  deorsumduction  were  less  tuan  i°. 
Looking  either  up  or  down  was  fatiguing.  The  condition 
found,  the  remedy  was  at  hand  in  the 

Ceiling-to-floor  Exercise 
of  the  superior  and  inferior  recti.  The  patient  was  directed 
to  stand  near  one  wall  of  a  room  of  usual  size,  and  to  se- 
lect some  mark  on  the  ceiling  near  the  opposite  wall  for  up- 
ward fixation,  at  the  same  time  placing  a  piece  of  coin,  a 
thimble,  or  some  other  object  on  the  floor  four  feet  in  front 
of  her  for  downward  fixation.  Standing  erect,  with  head 
set  as  for  vision  straight  ahead,  she  was  directed  to  look  at 
the  chosen  mark  on  the  ceiling  for  a  moment  and  then  at 
the  object  on  the  floor,  alternating  from  the  one  to  the  other 
every  two  or  three  seconds,  for  a  length  of  time  short  of  fa- 
tigue. She  was  directed  to  repeat  the  exercise  two  or  three 
times  a  day,  never  longer  than  ten  minutes  at  a  time.  Her 
improvement  began  at  once,  and  has  progressed  satisfacto- 
rily. Within  two  weeks  her  sursumduction  and  deorsum- 
duction were  2°.  There  can  be  no  doubt  that  her  improve- 
ment was  a  propte?'  hoc  and  not  a  post  hoc.  The  treatment 
was  rational:    it  proved  efficient.     Several  similar  cases  of 


AND   STHENIC   AND   ASTHENIC    HETEROPHORIA.  169 

less   severity   have   been  observed  since  the  first  one,  and 
have  been  benefited  by  the  ceiling-to-floor  exercise. 

Prismatic  exercise  of  the  superior  and  inferior  recti  could 
be  easily  resorted  to,  the  prisms  being  of  the  same  strength, 
their  axes  vertical  and  their  bases  toward  each  other  in 
the  rims,  after  the  style  of  the  Franklin  divided  lenses.  By 
slightly  elevating  and  lowering  the  frame,  the  patient  could 
be  made  to  look  at  a  light  across  the  room  alternately 
through  the  upper  and  lower  prisms.  This  raising  and  low- 
ering of  the  frames  should  be  rhythmic.  The  prismatic  ex- 
ercise cannot  sui-pass,  if  equal,  the  ceiling-to- floor  exercise. 

Asthenic  vertical  orthophoria  may  coexist  with  a  similar 
condition  of  the  lateral  recti  muscles,  and  often  does  com- 
plicate an  asthenic  exophoria.  In  either  case  a  part  of  the 
treatment  should  be  a  combination  of  the  ceiling-to-floor  and 
the  wall-to-wall  exercise,  chano-ino;  from  the  one  to  the  other 
every  half  minute  or  minute,  thus  continuing  for  ten  or  more 
minutes. 

Sthenic  and  Asthenic  Heterophoria 
are  not  products  of  the  imagination,  but  they  have  an  actual 
existence,    the    importance    of    which,   from   a  therapeutic 
standpoint,  should   not  be  ignored.     To  confound  them  in 
diagnosis  is  to  err  in  treatment. 

Sthenic  Exophoria 
is  a   common   condition,   and   may  be  readily    determined. 
The   phorometer  shows  exophoria  in  both  the  far  and  the 


I70  STHENIC   AND   ASTHENIC   ORTHOPHORIA, 

near  tests;  and  abduction  is  8°  or  more.  The  plan  of  treat- 
ing these  cases  must  be  decided  upon  after  carefully  weigh- 
ing the  results  obtained  by  both  the  phorometer  and  the  ab- 
duction. However  great  may  be  the  exophoria  far  and  near, 
if  the  abduction  is  8°,  nothing  should  be  done  to  the  externi. 
A  partial  tenotomy  would  do  harm,  and  any  exercise  of  these 
muscles  would  only  increase  the  trouble.  Attention  should 
be  given  only  to  the  interni.  Much  may  be  accomplished 
by  rhythmic  exercise,  by  means  of  the  exorphoric  set  of 
prisms ;  or  by  looking  at  a  lighted  wax  candle  as  it  is  moved 
from  arm's  length  to  within  six  inches  of  the  eyes,  following 
this  at  once  by  looking  at  some  distant  object,  repeating  the 
process  several  times  at  each  sitting;  or  by  the  method  of 
using  strong  prisms,  advocated  by  Gould.  The  success  of 
either  of  these  plans,  or  of  all  combined,  will  depend  on 
the  quantity  of  the  exophoria  and  on  the  age  of  the  individ- 
ual patient;  the  smaller  the  error  and  the  younger  the  pa- 
tient, the  more  rapid  will  be  the  cure.  Failing  to  cure  with 
the  exercise,  only  one  thing  remains  to  be  done — viz.,  short- 
ening or  folding  one  or  both  interni.  After  this  operation, 
if  a  small  part  of  the  old  error  remains  uncorrected,  the  ex- 
ercise treatment  may  be  resumed  with  the  prospect  of  com- 
pleting the  cure. 

If,  in  a  case  of  sthenic  exophoria,  the  abduction  is  more 
than  8°,  another  indication  for  treatment  presents  itself. 
This  indication  is  for  a  partial  tenotomy  of  one  or  both  ex- 


AND    STHENIC   AND   ASTHENIC    HETEROPHOR1A.  171 

terni,  and  this  should  be  done  without  temporizing  with  any 
method  of  exercising  the  interni.  The  operation  should  be 
so  carefully  done  as  never  to  reduce  the  abduction  below  8°. 
Often  a  partial  tenotomy  of  both  externi  will  produce  the 
desired  result,  the  establishment  of  sthenic  orthophoria. 
Failing  in  this,  rhythmic  exercise  of  the  interni  will  complete 
the  cure  in  many  cases,  though  occasionally  the  interni  must 
be  strengthened  by  shortening  one  or  both.  In  the  man- 
agement of  these  cases  we  have  at  our  command  partial  te- 
notomies of  the  externi,  rhythmic  exercise  of  the  interni,  and 
shortening  of  the  interni. 

Asthenic  Exophoria. 
In  this  condition  the  phorometer  will  show  exophoria,  in 
the  far  and  near  tests,  assciated  with  abduction  less  than  8°. 
In  these  cases  the  abduction  sometimes  falls  as  low  as  30, 
and  frequently  will  be  as  low  as  50  or  6°.  In  the  manage- 
ment of  these  cases  a  partial  tenotomy  of  the  externi  can  do 
only  harm,  and  the  shortening  of  the  interni  is  of  doubtful 
propriety.  The  former  operation  will  never  have  to  be 
done ;  the  latter  may  become  necessary,  but  in  these  cases 
it  becomes  a  matter  of  great  delicacv.  Two  methods  of  ex- 
ercise  should  be  resorted  to  daily  in  these  cases,  their  con- 
joined use  promising  the  greatest  good.  The  first  is  rhyth- 
mic exercise  of  the  interni  by  means  of  the  exophoric  set  of 
prisms;   the  second  is  the  wall-to-wall  exercise  of  both  the 


172  STHENIC   AND   ASTHENIC   ORTHOPHORIA, 

interni  and  the  externi,  as  advised  for  the  management  of 
asthenic  orthophoria. 

In  the  beginning  of  our  study  of  this  condition  two  years 
ago,  the  patient  was  directed  to  place  the  prisms  for  exercis- 
ing the  interni  at  one  time  in  the  twenty-four  hours,  and  at 
another  time  placing  them  for  the  exercise  of  the  externi. 
Out  of  this  method  grew  Dr.  Price's  double  prism  arrange- 
ment for  exercising  all  the  lateral  muscles  at  the  same  sitting. 
This  is  a  device  of  no  mean  merit. 

It  was,  doubtless,  in  cases  of  asthenic  exophoria  that  Dr. 
Park  obtained  his  good  results  from  having  his  patients  look 
from  side  to  side,  as  set  forth  in  his  paper  read  before  the 
Section  of  Ophthalmology,  A.  M.  A.,  at  Baltimore,  May, 
1895.  Certainly  this  method  could  do  no  good  in  cases  of 
sthenic  exophoria. 

Sthenic  Esophoria 
is  not  so  common  as  sthenic  exophoria.  The  phorometer 
shows  esophoria  in  the  far  and  near  tests,  and  the  adduction 
is  400  or  more.  While  partial  tenotomies  of  the  interni  may 
become  necessary  in  order  that  these  cases  may  be  cured, 
other  means  ought  first  to  be  tried,  except  in  cases  with  a 
high  degree  of  the  error.  The  other  available  means  are: 
First,  the  full  correction  of  a  coexisting  hypermetropia,  with 
or  without  astigmatism,  thus  curing  the  pseudo-esophoria; 
secondly,  the  rhythmic  exercise  of  the  externi  by  means  of  the 
esophoric  set  of  prisms.     This  failing,  a  partial  tenotomy  of 


AND   STHENIC   AND   ASTHENIC    HETEROPHORIA.  1 73 

the  interni  should  be  done,  if  adduction  is  above  the  nor- 
mal, while  shortening  of  the  externi  should  be  done  if  ad- 
duction is  only  normal.  After  either  of  these  operations  has 
been  done,  if  only  a  small  quantity  of  the  original  error  re- 
mains, the  cure  may  be  completed  by  rhythmic  exercise  of 
the  externi.  In  the  higher  errors,  the  operator  may  have  to 
perform  a  partial  tenotomy  on  both  interni,  and  make  a  short- 
ening operation  on  both  externi,  and  then  find  something  for 
rhythmic  exercise  to  accomplish. 

Asthenic  Esophoria. 
In  this  the  phorometer  shows  esophoria  in  the  near  and  far 
tests,  and  the  adduction  is  below  normal.  In  discussing 
sthenic  esophoria  we  have  placed  the  normal  adduction 
power  at  400,  which  cannot  be  far  from  right.  The  adduc- 
tion in  asthenic  esophoria  may  drop  as  low  as  200,  but  in 
most  cases  that  have  been  observed  it  has  been  between  300 
and  400.  A  low  adduction  in  esophoria  is  necessarily  as- 
sociated with  very  low  abduction,  which  should  be  tested. 
The  treatment  of  this  condition  should  be  by  means  of  gym- 
nastic exercise  alone,  at  least  for  a  long  while;  and  at  no 
time  should  an  operation  on  the  interni  be  considered. 
Each  of  two  kinds  of  exercise  should  be  resorted  to  once  or 
twice  a  day.  The  externi  should  be  exercised  by  the  eso- 
phoric  set  of  prisms,  and  both  the  externi  and  interni  should 
be  exercised  by  the  wall-to-wall  method.  These  failing  to 
accomplish  all  we  would  desire,  a  shortening  of  one  or  both 


174  STHENIC   AND   ASTHENIC    ORTHOPHORIA, 

externi  should  be  done.  The  object  of  the  shortening 
would  be  the  production  of  asthenic  orthophoria,  which 
must  be  cured  by  the  wall-to-wall  exercise  or  by  means  of 
the  double  prisms.  In  asthenic  esophoria,  a  partial  tenoto- 
my of  an  internal  rectus  would  result  in  harm,  and  should 
never  be  done. 

Sthenic  Hyperphoria. 

In  this  the  phorometer  shows  the  hyperphoric  condition  to 
exist,  and  measures  its  quantity.  There  is  in  these  cases  a 
sursumduction  of  the  hyperphoric  eye  and  a  deorsumduc- 
tion  of  the  cataphoric  eye  of  30  or  more.  In  those  cases  in 
which  the  sursumduction  of  the  hyperphoric  eye  is  only  30, 
the  normal,  the  treatment  should  be  by  exercise  alone,  to  be 
accomplished  by  the  use  of  the  hyperphoric  set  of  prisms. 
A  tenotomy  of  the  superior  rectus  of  the  hyperphoric  eve 
would  give  quick,  but  temporary,  relief;  but  if  an  operation 
is  to  be  done  at  all  in  these  cases,  it  should  be  the  shorten- 
ing of  the  inferior  rectus  of  the  hyTJerphoric  eye.  A  mus- 
cle that  has  onlv  the  normal  amount  of  intrinsic  strength,  as 
shown  by  the  duction  test,  should  be  allowed  to  retain  it. 

In  cases  of  sthenic  hyperphoria  with  sursumduction  of 
more  than  30,  the  first  indication  is  a  partial  tenotomy  of  the 
superior  rectus  of  the  hyperphoric  eye,  but  it  should  be  done 
so  as  not  to  reduce  its  duction  power  below  the  normal.  If 
there  still  remains  a  good  deal  of  hyperphoria,  and  the  deor- 
sumduction  of  the  cataphoric  eye  is  40  or  more,  a  partial 


AND   STHENIC   AND   ASTHENIC    HETEROPHORIA.  1 75 

tenotomy  of  its  inferior  rectus  may  be  done,  but  it  would 
probably  be  better  to  do  a  shortening  operation  on  the  in- 
ferior rectus  of  the  hyperphoric  eye.  One  or  more  opera- 
tions having  been  done,  whatever  hyperphoria  may  remain 
should  be  cured  by  means  of  the  hyperphoric  set  of  prisms. 

Asthenic  Hyperphoria 
is  a  very  common  condition.  The  degree  of  hyperphoria 
shown  by  the  phorometer  is  not  great,  rarely  more  than 
j4°i  while  the  sursumcluction  of  the  hyperphoric  eye  and 
the  deorsumduction  of  the  cataphoric  eye  are  below  the  nor- 
mal, often  as  low  as  2°,  and  sometimes  not  being  more  than 
i°.  Only  exercise  of  the  superior  and  inferior  recti  should 
be  considered  in  these  cases.  Each  of  two  methods  should 
be  resorted  to  once  or  twice  a  day.  At  one  sitting  the 
inferior  rectus  of  the  hyperphoric  eye  and  the  superior 
rectus  of  the  cataphoric  eye  should  be  exercised  by  means 
of  the  hyperphoric  prisms ;  the  next  exercise  should  be  of 
all  the  vertically  acting  muscles  by  means  of  the  ceiling- 
to-floor  method.  The  object  of  the  prism  exercise  is  to 
develop  the  condition  of  asthenic  vertical  orthophoria,  while 
the  aim  of  the  ceiling-to-floor  exercise  is  to  convert  the  as- 
thenic into  sthenic  vertical  orthophoria. 

Esophoria  in  the  far  and  exophoria  in  the  near  is  always 
an  asthenic  condition,  and  should  be  treated  by  prismatic 
exercise  and  by  the  wall-to-wall  method.  The  prism  exer- 
cise should  be  by  means  of  the  Price  double  prisms,  those 


I76  STHENIC    AND    ASTHENIC    ORTHOPHORIA. 

above  to  be  half  the  strength  of  those  below.  The  aim  in 
view,  when  using  the  prisms,  is  the  development  of  asthenic 
lateral  orthophoria,  while  the  wall-to-wall  exercise  is  to  con- 
vert the  asthenic  into  sthenic  orthophoria.  No  operation 
should  ever  be  done  on  these  cases. 


CHAPTER  IX. 

CAN   PRESBYOPIA   BE    DEFERRED    BY    RHYTH- 
MIC EXERCISE  OF  THE   CILIARY  MUSCLES?* 

One  of  two  conditions,  or  possibly  the  two  combined,  con- 
stitute the  causation  of  old  sight:  the  one,  loss  of  ciliary 
power;  the  other,  loss  of  elasticity  of  the  crystalline  lens. 
That  either  of  these  conditions  existing  alone  could  cause 
old  sight  none  can  doubt;  that  the  two  conditions  coexist  in 
well-advanced  cases  is  a  matter  easily  believed.  Lost  elas- 
ticity of  the  lens  would  lead  to  inactivity,  and  consequent 
atrophy,  of  the  ciliary  muscle ;  while  diminished  or  lost  cili- 
ary action  would  cause  suspension,  if  not  loss,  of  lens  elas- 
ticity. 

That  the  leading  cause  of  old  sight  is  failure  of  ciliary 
power  we  think  may  be  proved;  and  if  this  is  true,  simple 
and  scientific  means  for  deferring  the  onset  of  presbyopia 
may  be  brought  into  use.  Rhythmic  exercise  can  be  as 
readily  effected  in  the  ciliary  muscle  as  in  any  of  the  extra- 
ocular muscles.  Will  this  exercise  develop  the  power  of 
these  muscles  that  are  under  the  direct  control  of  the  guid- 
ing sensation,  the  common  master  of  all  the  extra-  and  intra- 
ocular muscles? 

*Read  in  the  Nashville  Academy  of  Medicine  January,  1S94 

12  _  (177) 


178  PRESBYOPIA   AND   THE    CILIARY   MUSCLES. 

That  involuntary  muscular  fibers  can  be  increased  in  size 
and  augmented  in  power,  as  a  result  of  effort  to  overcome 
obstruction,  is  a  matter  of  common  acceptance,  so  far  as 
the  heart  and  bladder  are  concerned.  In  mitral  stenosis  it  is 
well  known  that  the  walls  of  the  left  auricle  become  hyper- 
trophied  and  more  powerful,  so  that  it  may  send  the  blood 
through  the  narrowed  opening  into  the  ventricle;  in  like 
manner,  when  there  is  obstruction  at  the  aortic  opening,  the 
walls  of  the  ventrical  become  hypertrophied  and  more  pow- 
erful. 

When  the  prostate  gland  is  enlarged  or  there  is  stricture 
of  the  urethra,  impeding  the  flow  of  urine,  the  muscular 
fibers  in  the  walls  of  the  bladder  are  increased  in  size,  and 
become  much  more  powerful,  so  as  to  be  able  to  force  the 
flow.  It  will  be  conceded  that  this  muscle  development  in 
heart  and  bladder  results  from  effort  to  overcome  obstruc- 
tion. 

Displacement  of  images  by  prisms  and  blurred  images  by 
means  of  concave  lenses  are  obstructions  which,  if  not  too 
great,  will  be  overcome  by  muscular  action,  the  former  by 
action  of  the  recti  muscles,  the  latter  by  action  of  the  ciliary 
muscle.  Many  observers  have  already  acknowledged  that 
rhythmic  exercise  of  the  recti  muscles,  by  means  of  prisms, 
and  of  the  obliques  by  means  of  cylinders  properly  placed, 
not  only  increases  their  power,  but  at  the  same  time  dispels 
the  nervous  phenomena  associated  with  and  dependent  on 


PRESBYOPIA  AND   THE   CILIARY   MUSCLES.  1 79 

their  former  weakness.  If  the  ciliary  muscles  can  be  de- 
veloped by  rhythmic  exercise,  then  concave  lenses,  not  too 
strong,  used  rhythmically,  but  not  too  long  at  a  time,  may 
be  the  means  of  deferring  old  sight  to  five  or  ten,  or  even 
more,  years  beyond  the  now  common  age  of  its  onset — 
about  the  age  of  forty-five  years. 

As  in  developing  the  recti  and  oblique,  so  in  the  develop- 
ment of  the  ciliary  muscles,  the  power  to  overcome  obstruc- 
tion should  never  be  taxed  to  anything  like  its  fullest  capac- 
ity. Gentle  contraction  and  relaxation,  rhythmic  in  order, 
continued  five  to  ten  minutes  and  repeated  two  or  three 
times  in  the  twenty-four  hours,  must  result  in  giving  tone  to 
the  ciliary  muscle.  The  time  of  life  for  beginning  the  ex- 
ercise, and  the  strength  of  concave  lenses  to  use,  are  matters 
that  must  be  settled  by  observation  and  experience.  As  a 
preliminary  to  the  treatment  of  failing  accommodation,  all 
existing  focal  errors  should  be  corrected,  and  this  cor- 
rection should  be  worn  behind  the  exercise  lenses  at 
each  sitting.  It  is  my  present  judgment  that  — .50  D. 
spherical  lenses,  properly  centered,  will  be  the  most  use- 
ful. The  patient  should  be  seated  fifteen  to  twenty  feet 
from  a  lighted  candle,  lamp  or  gas  jet,  and  should  look  at 
the  same  through  the  concave  lenses  five  seconds,  and  then 
raise  them  for  a  period  of  five  seconds,  and  so  on  to  the  end 
of  the  sitting.  It  is  evident  that,  with  the  focal  correction 
on  when  needed,  the  image  of  the  flame  is  sharp,  satisfying 


I  SO  PRESBYOPIA  AND   THE   CILIARY   MUSCLES. 

the  guiding  sensation  without  ciliary  action.  The  moment 
the  weak  concave  lenses  are  lowered  the  image  is  blurred, 
and  at  once  the  ciliary  muscle  is  called  into  action,  to  again 
return  to  a  state  of  rest  the  moment  they  are  raised.  Thus 
contraction  and  relaxation  are  easily  induced.  In  this  way 
the  nutrition  of  the  muscle  should  be  improved  and  its 
power  enhanced  or  maintained.  The  age  at  which  to  begin 
the  exercise,  as  a  rule,  need  not  be  under  forty  nor  over 
forty-three  years,  and  it  should  be  continued  as  long  as  the 
proper  reading  distance  is  preserved. 

The  question  would  naturally  arise  in  the  mind  of  the  pa- 
tient as  well  as  that  of  the  practitioner,  "Can  any  injury  come 
from  the  treatment?"  The  nutrition  of  the  ciliary  body  is 
from  the  blood  that  circulates  in  it.  Nothing  is  more  reason- 
able than  that  gentle,  rhythmic,  and  periodic  exercise  of  the 
ciliary  muscle  would  improve  the  nutrition  of  the  ciliary 
body,  just  as  the  nutrition  of  other  muscles  is  improved  by 
proper  exercise.  No  harm,  then,  could  come  to  the  muscle 
as  a  result  of  the  proposed  gymnastic  exercise.  May  we 
fear  unfavorable  change  in  the  lens  as  a  consequence  of  this 
exercise  of  the  ciliary  muscle?  It  is  generally  conceded 
that  the  lens  gets  its  nourishment,  by  the  process  of  osmosis, 
from  the  blood  circulating  in  the  ciliary  body.  It  must  be 
acknowledged  that  the  better  the  nutrition  of  the  lens,  the 
more  likely  will  it  retain  its  two  very  important  properties, 
transparency  and  elasticity.     It  cannot  be  denied  that  the 


PRESBYOPIA  AND   THE   CILIARY   MUSCLES.  l8l 

better  the  nutrition  of  the  ciliary  body,  the  healthier  will 
be  the  crystalline  lens.  We  must  conclude  that,  if  the  ex- 
excise  would  improve  the  condition  of  the  ciliary  body,  it 
would  at  the  same  time  have  a  tendency  to  improve  the  nu- 
trition of  the  lens,  whereby  the  latter  would  be  only  the  more 
certain  to  continue  both  transparent  and  elastic.  Thus  not 
only  may  old  sight  be  deferred,  but  also  the  development  of 
cataract  may  be  prevented.    . 

May  there  not  be  such  a  condition  as  congenital  weakness 
of  the  ciliary  muscle?  If  so,  have  we  not,  in  the  proposed 
rhythmic  exercise,  by  means  of  concave  spherical  lenses,  a 
source  of  power  to  the  weak  muscles? 

Since  reading  the  above  paper  before  the  Academy  of 
Medicine,  continued  observation  and  experience  have  so 
far  been  confirmatory  of  the  correctness  of  the  thoughts 
contained  therein.  As  to  the  last  paragraph  of  the  paper,  I 
am  sure  that  there  is  a  great  deal  more  in  it  than  I  thought 
there  was  at  the  time  it  was  penned.  Not  only  may  there  be 
a  congenital  or  an  acquired  weakness  of  both  ciliary  mus- 
cles, but  there  are  undisputed  cases  of  greater  weakness  on 
the  part  of  one  muscle  than  on  the  part  of  the  other  in  the 
same  pair  of  eyes.  For  instance,  one  eye  ma)-  have  an 
accommodative  power  of  4  D.,  while  the  other,  under  sim- 
lar  tests,  would  show  an  accommodative  power  of  5  or 
more  D. 

When  there  is  a  similar  want  of  power  in  the  two  muscles 


l82  PRESBYOPIA  AND   THE    CILIARY   MUSCLES. 

they  both  should  be  exercised  at  the  same  time  after  the 
method  set  forth  in  the  paper.  If  there  is  a  difference  in  the 
power  of  the  two  muscles,  the  eye  having  the  stronger  mus- 
cle should  be  covered  while  the  other  muscle  is  exercised  by 
means  of  the  concave  sphere. 

If  any  case  of  hypermetropia  associated  with  exophoria  is 
more  comfortable  by  wearing  the  convex  glasses  correcting 
same,  that  of  itself  is  an  evidence  of  either  a  congenital  or 
an  acquired  weak  condition  of  the  ciliary  muscles.  These 
cases  are  sometimes,  though  rarely,  met  with.  Such  a  case 
furnished  with  concave  glasses  to  be  worn  continuously,  as 
is  sometimes  done  by  opticians,  would  be  made  worse  and 
not  better;  while  if  the  ciliary  muscles  were  stronger,  the 
concave  glasses  making  the  case  more  hypermetropic,  but  at 
the  same  time  lessening  the  complicating  exophoria,  would 
bring  relief  to  the  patient. 


CHAPTER  X. 

THE  LAW  OF  PROJECTION  AND  THE  ARTIFICIAL 
AND  NATURAL  CAUSES  THAT  MODIFY  IT. 

In  the  March  (1893)  issue  of  the  Ophthalmic  Record  I 
announced  what  I  believed  to  be  the  law  of  projection  in 
the  following  words:  "  What  is  true  of  one  part  of  the  ret- 
ina, as  to  projection,  must  be  true  of  all  parts.  In  the  field 
of  vision,  that  object  is  most  distinctly  seen  which  is  on  the 
line  of  the  visual  axis  and  consequently  throws  its  image  on 
the  yellow  spot.  The  visual  axis  is  a  line  vertical  to  the  yel- 
low spot."  By  the  aid  of  the  accompanying  cut  I  pro- 
pose to  show  that  the  law  of  projection  is  this :  Every  object 
seen  must  be  on  a  line  vertical  to  that  -part  of  the  retina  re- 
ceiving the  impress  of  the  light,  regardless  of  the  direction 
of  the  axial  ray  in  the  eye.  In  the  cut,  the  star-shaped  Fig- 
ures 1,2,  and  3  represent  sources  of  light.  The  eye  is  rep- 
resented as  being  fixed  on  Figure  3,  from  which  extends  the 
line  i  through  the  eye  to  the  macula  lutea.  This  line  repre- 
sents the  coinciding  visual  axis  and  the  central  ray  of  the 
cone  of  light,  and  is  conceded  to  be  vertical  to  the  retina  at 
this    point.     While  the  vision   is  fixed  on  Figure  3,  Figure 

1,  which  is  900  from  Figure  3,  makes  it  impress  on  the  nasal 

(183) 


1 84 


THE    LAW    OF    PROJECTION: 


side  of  the  retina  900  from  the  macula.     That  Figure  1  may 
be  seen  at  all  it  must  send  rays  of  light  through  the  cornea  and 

3 


pupil  into  the  eye.  The  incident  ray  is  b  c,  while  c  d  is  the 
refracted  ray  (for  convenience  of  study  the  combined  re- 
fraction of  the  cornea  and  the  lens  may  be  represented  as 


CAUSES    THAT    MODIFY    IT.  1 05 

taking  place  at  the  corneal  surface).  Its  impress  is  made 
on  the  retina  at  d.  In  obedience  to  the  law,  the  source  of 
the  light  is  projected  on  the  line  a  d,  which  is  vertical  to  the 
retina  at  d.  In  the  same  manner,  as  is  shown  in  the  cut, 
Figure  2,  to  be  seen,  must  send  light  through  the  cornea  and 
pupil  into  the  eye,  that  it  may  make  its  impress  on  the  retina. 
The  incident  ray  isy"  g  and  the  refracted  ray  g  h.  The 
source  of  the  light  is  at  once  projected  on  the  line  e  k,  which 
is  vertical  to  the  point  of  the  retina  at  h.  As  is  shown  in  the 
cut,  the  three  lines  of  direction  (projection)  cross  one  an- 
other in  the  center  of  retinal  curvature,  and  are  therefore 
radii  prolonged. 

In  the  perfect  eye  all  that  we  claim  for  the  macula  lutea, 
as  to  projection,  must  be  granted.  This  being  granted,  it 
can  be  easily  made  clear  that  all  points  of  the  retina  obey 
the  same  law  of  projection.  The  arc  i-j,  on  which  are  lo- 
cated the  three  sources  of  light,  and  the  retinal  arcy  d,  on 
which  the  images  of  these  objects  fall,  are  each  900,  and 
parts  of  concentric  circles,  the  common  center  being  at  k. 
Since  objects  are  seen  on  straight  lines,  and  Figure  1  is  at  a 
right  angle  to  Figure  3,  its  image  on  the  retina  at  d  must  be 
just  900  fromy,  the  macula,  where  falls  the  image  of  Figure  3. 
Thus  we  can  understand  how  objects  situated  on  any  part 
of  the  arc  i-j  must  throw  their  images  on  corresponding 
points  of  the  retinal  arcy"  d.  If  further  confirmation  were 
needed,  we  have  it  in  the  fact  that,  when  the  eye  sees  two 


l86  THE    LAW    OF    PROJECTION: 

lights,  represented  in  the  cut  by  Figures  3  and  I,  if  the 
visual  axis  is  made  to  sweep  the  arc  from  Figure  3  to  fix  on 
Figure  1,  while  the  attention  is  fixed  on  Figure  3,  the  latter 
is  not  seen  to  move,  thus  showing  that  every  part  of  the  ret- 
inal arc  (from  j  to  point  of  retina  cut  by  line  a  d)  over 
which  the  image  of  Figure  3  has  passed,  obeys  the  same  law 
of  projection  as  that  governing  the  macula. 

From  the  above  reasoning  we  deduce  the  following  con- 
clusions: The  line  of  direction  is  a  prolonged  radius  of  ret- 
inal curvature ;  the  center  of  direction  k  is  the  center  of  ret- 
inal curvature;  the  visual  angle  is  located  at  k,  and  is  un- 
alterable in  position,  but  may  be  changed  in  size  by  properly 
centered  convex  and  concave  lenses ;  the  visual  angle  being 
nearer  the  retina  than  formerly  supposed,  retinal  images 
must  be  correspondingly  smaller;  on  either  side  of  the  vis- 
ual axis,  the  incident  and  refracted  ray,  with  the  line  of  di- 
rection as  a  base,  form  a  triangle,  the  apex  looking  toward 
the  visual  axis,  the  angle  at  the  apex  growing  larger  as  the 
source  of  the  light  approaches  the  visual  axis. 

That  the  law  of  projection  is  susceptible  of  modification 
by  conditions  that  may  be  brought  into  existence  artificially, 
and  bv  at  least  two  natural  conditions,  cannot  be  denied. 
Other  laws  of  nature  are  subject  to  similar  modifications. 
In  obedience  to  the  law  of  gravitation,  everything  within  the 
range  of  the  influence  of  the  earth  is  drawn  toward  its  cen- 
ter.    If  other  forces  could  not  modify  the  law  of  gravitation, 


CAUSES    THAT    MODIFY    IT.  1 87 

all  objects  on  the  earth  would  be  fixed,  and  any  object  in 
the  atmosphere  would  be  drawn  toward  the  earth  in  a 
straight  line.  If  a  ball  be  allowed  to  drop  from  the  hand,  it 
goes  in  a  straight  line  to  the  earth ;  if  it  be  thrown  by  the 
exercise  of  the  muscular  power  of  the  arm,  it  must  come  to 
the  earth,  but  in  doing  so  it  describes  a  curve.  The  muscu- 
lar force  has  thus  modified  the  law  of  gravitation. 

The  modifications  of  the  law  of  projection  take  place  only 
where  there  are  two  eyes.  With  a  lighted  candle  twenty 
feet  distant,  one  eye  may  be  closed  while  the  other  is  fixed 
on  the  blaze.  Interposing  a  prism  of  6°,  base  out,  before 
the  open  eye,  the  candle  is  displaced  toward  the  opposite 
side,  where  it  can  be  readily  fixed  by  a  contraction  of  the  in- 
ternal rectus  shifting  the  visual  axis ;  but  the  line  of  projec- 
tion remains  vertical  so  long  as  the  fellow-eye  remains 
closed.  On  opening  the  other  eye  two  candles  are  seen,  but 
they  immediately  run  into  each  other,  in  obedience  to  the  law 
governing  the  recti  muscles,  causing  them  to  so  act  as  to 
place  the  macula  in  each  so  that  it  may  receive  the  image  of 
the  candle.  In  this  case  the  line  of  projection  of  the  eye 
before  which  the  prism  is  held  does  not  pass  through  the 
center  of  direction,  k,  but  on  the  temporal  side  of  it.  Re- 
move the  prism,  and  at  once  the  law  of  projection  reasserts 
itself.  The  sensorium  is  so  influenced  by  the  disturbing  el- 
ement (the  prism)  that,  at  one  trial,  both  lights  seem  to  move 
toward  each  other;  at  another  trial,  the  true  candle  appears 


i88 


THE    LAW    OF    PROJECTION: 


to  move  to  the  false;  and  again  the  false  to  the  true  candle. 
It  is,  at  the  same  time,  evident  that  the  line  of  projection  is 
displaced  only  in  the  eye  before  which  the  prism  is  held. 
By  reversing  the  prism  the  line  of  direction  can  be  made  to 
pass  on  the  nasal  side  of  the  center  of  direction,  k. 

In  a  similar  way  it  can  be  shown  that  cylinders  placed  be- 
fore non-astigmatic  eyes  obliquely  in  opposite  directions,  or, 
if  in  the  same  direction,  more  obliquely  before  one  eye  than 
the  other,  cause  a  modification  of  the  law  of  projection.  In 
the  case  of  prisms,  the  modification  of  the  law  of  projection 
is  effected  by  the  contraction  of  the  recti  in  fusing  the  im- 
ages; in  the  case  of  the  cylinders,  the  contraction  of  the  ob- 
liques, for  the  purpose  of  fusing  the  images,  causes  the  mod- 
ification of  the  law  of  projection. 

Prisms  and  cylinders  constitute  the  two  artificial  means 
that  disturb  the  law  of  projection.  Decentration  of  the  mac- 
ula in,  out,  up,  or  down,  but  in  opposite  directions  in  the 
two  eyes,  or  if  in  the  same  direction,  the  one  being  decen- 
tered  more  than  the  other;  and  oblique  astigmatism,  the 
obliquity  being  in  opposite  directions,  or  if  in  the  same  di- 
rection, more  oblique  in  the  one  eye  than  in  the  other,  con- 
stitute the  two  natural  means  that  disturb  the  law  of  projec- 
tion. 

Any  condition  disturbing  the  law  of  projection  is  an  unde- 
sirable thing,  and  should  be  remedied.  In  cases  where  there 
is  decentration  of  the  maculae,  the  law  of  projection  can  be 


CAUSES    THAT    MODIFY    IT.  1 89 

given  full  play  only  by  means  of  correct  prisms  properly 
placed;  likewise  in  oblique  astigmatism  the  majesty  of  the 
law  can  be  asserted  only  through  the  means  of  correcting 
cylinders  properly  placed.  In  determining  both  of  these 
conditions  the  ophthalmometer  is  invaluable. 

Have  we  not  in  this  an  explanation  why,  in  some  cases  of 
heterophoria,  prisms  are  a  source  of  much  comfort,  while, 
in  other  cases,  they  add  to  the  discomfort?  In  the  light  of 
the  reasoning  had,  it  seems  clear  that  when  the  maculae  are 
properly  centered,  whatever  form  of  heterophoria  may  ex- 
ist, be  it  of  high  or  low  degree,  it  would  not  be  wise  to  at- 
tempt its  relief  by  means  of  prisms.  Prisms  should  be  pre- 
scribed for  that  form  of  heterophoria  only  where  there  is  ev- 
idence of  decentration  of  the  maculae. 

Again,  the  law  of  projection  as  herein  announced  set- 
tles the  question  of  corresponding  parts  of  the  two  retinae. 
If  the  two  visual  axes  be  fixed  on  an  object,  it  can  be  demon- 
strated that  another  object  on  the  monoscopter,  to  the  right, 
will  throw  an  image  on  the  nasal  half  of  the  right  retina  the 
same  distance  from  the  macula  as  the  image  in  the  left  eye 
will  be  from  the  macula  on  the  temporal  half  of  the  retina. 
In  each  case  the  object  will  be  projected  on  lines  vertical  to 
the  parts  of  the  two  retinae  receiving  the  impress.  These 
lines  of  projection,  intersecting  at  the  object,  make  it  appear 
as  one.  The  same  can  be  demonstrated  as  true  of  any  ob- 
ject situated  on  the  monoscopter. 


I9O  THE    LAW    OF    PROJECTION. 

The  law  of  direction,  as  herein  given,  affords  us  a  satis- 
factory and  scientific  answer  to  the  question :  Why  is  it  we 
see  objects  erect  when  we  know  their  images  are  inverted 
on  the  retina?  A  line  drawn  from  a  man's  head  to  the  cen- 
ter of  the  observer's  eye,  when  prolonged,  must  strike  the 
retina  as  many  degrees  below  the  horizontal  plane  of  the 
center  of  direction  as  the  head  of  the  observed  is  above  this 
plane;  and  in  like  manner  a  line  drawn  from  the  man's 
feet  through  the  center  of  the  observer's  eye,  when  pro- 
longed, must  strike  the  retina  at  a  point  as  many  degrees 
above  the  horizontal  plane  as  the  man's  feet  are  below  this 
plane.  The  rays  of  light  from  the  head  and  feet,  though 
not  coincident  with  the  lines  of  direction,  after  being  re- 
fracted make  their  impress  respectively  on  those  parts  of 
the  retina  which  we  have  already  pointed  out  as  being  con- 
nected, by  straight  lines  passing  through  the  center  of  direc- 
tion, with  the  head  and  the  feet.  In  obedience  to  this  law  we 
see  the  sides  of  the  object  the  reverse  of  those  of  the  image. 

Binocular  single  vision,  and  erect  objects  and  inverted 
images,  result  from  this  physical  law:  Every  object  seen 
must  be  on  a  line  vertical  to  that  part  of  the  retina  receiving 
the  impress  of  the  light. 


CHAPTER  XI. 

THE  MONOSCOPTER. 

We  have  both  a  line  and  a  surface  of  binocular  single  vis- 
ion. The  term  used  by  those  authors  who  speak  of  it  at  all 
is  "horopter  "  which  means  limit  of  vision.  Noyes  is  the 
only  one  of  the  several  writers  on  ophthalmology  in  my  pos- 
session who  speaks  of  the  horopter.  In  speaking  of  it  he 
says:  "The  horopter  is  a  line  which  represents  the  curve 
along  which  both  eyes  can  join  in  sight,  and  it  is  formed  in 
this  way:  As  the  eyes  fix  on  a  given  object  far  to  the  left 
side,  and  move  far  to  the  right  at  the  same  inclination  of  the 
visual  lines,  they  form  a  triangle  whose  apex,  as  it  passes 
from  left  to  right,  forms  the  horopter  curve  for  this  plane. 
If  the  movement  be  in  any  other  plane,  vertical  or  oblique, 
the  horopter  will  be  formed  in  the  same  way  for  that  plane. 
In  its  simplest  form,  as  explained  by  Johannes  Mueller,  it  is 
a  circle  which  passes  through  the  center  of  rotation  of  each 
eye,  and  through  the  apex  of  the  point  of  fixation  of  the  vis- 
ual lines."  If  it  be  granted  that,  by  the  expression  "  cen- 
ters of  rotation,"  Mueller  meant  the  centers  of  retinal 
curvature,  then  all  that  has  been  quoted  above  can  be  dem- 
onstrated as  true  mathematically;   and  yet  Noyes,  in  closing 

(191) 


I92  THE    MONOSCOPTER. 

the  paragraph,  says:  "This  statement  [of  Mueller]  is  not 
strictly  correct,  but  will  suffice  for  our  purposes."  Noyes's 
statement  and  that  of  Mueller  are  exactly  the  same  in  sub- 
stance. 

Before  entering  into  the  demonstration  of  the  line  and 
surface  of  single  seeing,  which  I  shall  name  the  monoscopter 
(fiovog,  single,  and  GxoTtEidV,  seeing),  a  name  chosen  after  a 
consultation  with  Prof.  George  W.  Jarman,  who  has  taught 
Greek  for  many  years,  I  will  quote  Noyes  a  little  further: 
"If  the  back  of  the  eyeball  be  divided  into  quadrants  by 
vertical  and  horizontal  planes  whose  intersection  shall  be  at 
the  fovea  centralis,  and  parallel  to  these  lines  we  mark  points 
one  tenth  of  a  millimeter  asunder,  and  then  suppose  the  two 
retinas  to  be  superimposed  upon  each  other  so  that  the  ver- 
tical and  horizontal  lines  shall  exactly  coincide,  the  points 
we  have  imagined  will  of  course  also  coincide.  The  coinci- 
dent points,  which  are  equidistant  from  the  center,  are 
spoken  of  as"  correspondent  points  of  the  two  retinas." 

What  I  have  quoted  from  Noyes  could  not  be  true  if  the 
law  of  projection,  as  published  in  No.  12,  Vol.  II.,  of  the 
Ophthalmic  Record,  were  not  the  truth. 

Believing  that  I  have  already  demonstrated*  that  the  law 
of  projection  (direction)  is,  "  Everything  seen  is  on  a  line 
vertical  to  the  part  of  the  retina  receiving  the  impress  of  the 

*See  Chapter  X. 


THE    MONOSCOPTER. 


193 


light  "  (all  lines  of  direction  cross  at  the  center  of  retinal 
curvature),  I  will  now  demonstrate  the 

Monoscopter. 
By  reference  to  the  accompanying  cut,  it  will  be  seen  that 


the  three  points  chosen  for  the  construction  of  the  circle  are: 
c,  the  point  of  fixation  of  the  two  eyes;  b,  the  center  of  ret- 


13 


194  THE    MONOSCOPTER. 

inal  curvature  of  the  left  eye;  and  d,  the  center  of  retinal 
curvature  of  the  right  eye.  This  line  of  single  seeing  is  in 
the  plane  of  the  visual  axes.  A  point  situated  anywhere  on 
this  line,  capable  of  sending  rays  of  light  into  the  two  eyes, 
must  be  seen  as  one  by  the  two  eyes.  The  visual  axis,  h  c, 
and  the  visual  axis,  g  c,  intersect  at  c,  therefore  the  point  c 
must  be  seen  as  one.  Point  a  on  the  circle  sends  rays  of 
light  (not  shown  in  the  cut)  into  both  eyes.  Those  in  the 
right  eye  strike  the  retina  at/7  those  in  the  left  eye,  at  j. 
The  visual  line  a  j  passes  through  the  point  b,  and  the  vis- 
ual line  a  f  passes  through  the  point  d.  Since  these  visual 
lines  intersect  at  a,  then  this  point  must  be  seen  as  one.  As 
is  seen,/  and/"  are  in  the  same  plane.  It  can  be  proven 
that/  is  just  as  far  on  the  nasal  side  of  the  yellow  spot  //,  as 
f  is  on  the  temporal  side  of  the  yellow  spot  g.  Since  the 
angle  a  b  c  is  equal  to  the  angle  h  b  /,  and  the  angle  a  d  c  is 
equal  to  the  angle  g  d  f,  it  only  remains  to  prove  that  the  an- 
gle a  b  c==  the  angle  a  d  c,  in  order  that  it  may  be  shown 
that/  and  f  are  correspondent  parts  of  the  two  retinae. 
The  angle  a  b  c  (an  inscribed  angle)  is  measured  by  half  the 
arc  a  c;  the  angle  a  d  c  (an  inscribed  angle)  is  measured 
by  half  the  arc  a  c.  Since  the  two  angles  a  b  c  and  a  d  c 
are  each  measured  by  half  the  same  arc,  a  c,  the  one  must 
be  equal  to  the  other.  Thus  is  proven  the  correctness  of 
Mueller's  definition  of  what  he  improperly  called  the  ho- 
ropter. 


THE    MONOSCOPTER.  I95 

Having  proven  the  line  of  binocular  single  seeing,  it  is 
easy  enough  to  demonstrate  the  surface  of  single  seeing, 
which  is  a  surface  of  revolution,  described  by  revolving  the 
circular  plane  a  b  d  e  c  on  its  cord  b  d,  while  the  eyes  re- 
main stationary.  This  surface  is  a  combination  of  a  concave 
sphere  and  a  concave  cylinder. 

My  private  student,  Dr.  Manning  Brown,  succeeded  in 
having  constructed  for  me  this  peculiar  concave  surface. 

It  is  interesting  to  note,  further,  that  all  angles  formed  by 
the  intersection  of  visual  lines  in  the  monoscopter  are  equal 
to  one  another.  The  angle  bad,  formed  by  the  visual  lines 
b  a  and  d  a,  is  equal  to  the  angle  bed,  formed  by  the  visual 
axes  b  c  and  d  c,  for  each  is  measured  by  half  the  arc  b  d. 
What  is  true  of  these  two  angles  is  true  of  any  angle  formed 
on  the  monoscopter  by  the  intersection  of  visual  lines. 
Thus  is  proven  to  be  correct  the  statement  quoted  from 
Noyes  in  the  beginning  of  this  demonstration,  if  he  meant, 
by  the  expression  "  same  inclination  of  the  visual  lines," 
that  the  angle  formed  by  the  intersection  of  the  visual  axes 
remains  the  same,  as  the  curve  is  being  described. 


PART   II. 


Contributions  to  Old  Studies. 


CHAPTER  I. 

HETEROPHORIA:  AND  A  SAFE  LINE  DRAWN  BE- 
TWEEN  OPERATIVE  AND  NON-OPERATIVE 
CASES;  AND  THE  AUTHOR'S  METHOD  OF  OP- 
ERATING.   

Of  the  several  theories  held  by  different  observers  as  to 
the  nature  of  heterophoria,  neither  one  may  be  absolutely 
correct  to  the  exclusion  of  the  others.  In  some  cases  one 
theory  may  be  correct;  in  other  cases,  another  theory;  and 
in  another  class  of  cases,  a  still  different  theory  would  be 
applicable. 

A  brief  review  of  the  different  explanations  of  hetero- 
phoria may  not  be  out  of  place  just  here.  One  view  is  that 
there  is  a  congenital  feebleness  of  one  muscle  as  compared 
with  its  opposing  muscle,  this  weakness  being  due  either  to 
the  fewness  of  the  muscular  fibers  entering  into  its  forma- 
tion or  to  its  faulty  attachment  to   the   sclera,  this  in  the 

(197) 


I98  HETEROPHORIA. 

weak  muscle  being  abnormally  far  from  the  corneo-scleral 
junction,  or  to  a  want  of  proper  innervation.  That  there 
can  be  truth  in  this  view  no  one  can  successfully  deny. 
There  can  be  no  case  of  heterophoria  in  which  this  theory 
will  not  explain  some  of  the  phenomena. 

Another  theory  denies  that  heterophoria  is  congenital. 
Its  advocates  teach  that  the  development  and  growth  of  the 
ocular  muscles  have  been  normal,  their  attachments  perfect, 
and  their  nerve  supply  all  that  could  be  desired.  They 
would  teach  us  that  some  irritation  in  or  about  the  eye,  or  in 
some  organ  remote  from  the  eye,  excites  a  spasm,  tonic  in 
its  nature,  in  one  of  a  pair  of  muscles,  thus  destroying  their 
harmonious  action.  This  spasm  existing  in  the  superior 
rectus  would  give  hyperphoria ;  in  the  internal  rectus,  eso- 
phoria;  in  the  external  rectus,  exophoria;  in  one  of  the  ob- 
liques, a  form  of  heterophoria  first  described  by  the  author 
of  this  paper.*  [To  this  condition  my  office  associate,  Dr. 
George  H.  Price,  has  since  applied  the  name  Cyclophoria.] 
This  condition  would  certainly  explain  some  of  the  phenom- 
ena seen  in  the  examination  of  any  case  of  heterophoria,  and 
will,  therefore,  always  have  its  advocates. 

The  third  theory  grants  that  congenitally  the  muscular 
apparatus  of  the  eyes  may  be  all  right,  just  what  is  claimed 
by  the  advocates  of  theory  No.  2;  and  yet  it  claims  that  the 

*  See  Arc/iives  of  Ophthalmology,  Vol.  XX.,  No.  1,  1891. 


HETEROPHORIA.  I99 

cause  of  heterophoria  is  congenital,  in  that  the  macula?  do 
not  occupy  corresponding  places  in  the  two  retinae.  A  con- 
genital displacement  of  the  macula  up  or  down  in  one  eye 
would  give  hyperphoria;  a  congenital  displacement  of  the 
macula  in  one  or  both  eyes,  outward,  would  give  esophoria; 
and  a  similar  displacement  inward  would  give  exophoria. 
This  theory  also  includes  the  idea  that  an  abnormal  placing 
of  the  eyes  in  their  orbits  can  cause  heterophoria.  If  one 
eye  (and  its  orbit)  occupies  a  lower  plane  than  its  fellow, 
there  necessarily  results  a  hyperphoria. 

If  any  other  theories  for  heterophoria  have  been  framed, 
they  have  not  come  under  my  observation.  Only  two  of 
these  theories  have  before  been  published  so  far  as  I  know. 
The  third  theory  being  a  deduction  of  my  own,  and  is  here 
given  for  what  it  may  be  worth. 

Something  can  be  said  for  and  against  all  of  these  views. 
Against  all  of  them  stands  the  one  fact  that,  in  many  cases 
of  horizontal  heterophoria,  wre  have  esophoria  for  distance 
and  exophoria  for  near. 

If  asked  which  of  the  three  I  accept,  I  would  answer  that 
I  believe  that  each  one  contains  a  germ  of  truth;  and  that, 
possibly,  the  conditions  included  in  each  coexist  in  certain 
cases. 

There  may  never  be  unanimity  of  opinion  as  to  the  nature 
of  heterophoria;  but  the  concession  that  such  a  thing  exists 
is  already  universal.     Heterophoria,  having  always  had  an 


200  HETEROPHORIA. 

existence,  will  always  continue  to  exist.  In  the  not  very  re- 
mote past  nothing  was  done  for  its  relief,  because  nothing 
was  known  of  its  existence.  Oculists  of  to-day  and  of  the 
future  must  combat  this  disturber  of  human  comfort. 

In  order  to  reach  a  conclusion  as  to  the  form  of  hetero- 
phoria,  and  the  amount  of  same  in  any  given  case,  and  how 
it  should  be  dealt  with,  two  or  more  of  the  several  tests  now 
known  should  be  resorted  to.  In  all  cases  it  is  my  custom, 
after  making  a  complete  correction  of  any  existing  error  of 
refraction,  to  resort  to  four  muscle  tests,  and  when  these  do 
not  clear  my  mind  of  doubt,  I  try  a  fifth  test.  [I  have  since 
learned  from  study  and  the  observation  of  cases  that  all 
tests  for  lateral  heterophoria  are  unreliable  while  the  eyes 
are  under  the  influence  of  a  mydriatic]  These  will  be  ex- 
plained in  the  order  in  which  I  take  them.  The  first  is  the 
Maddox  rod  test.  Providing  the  lenses  correcting  the  er- 
rors of  focus  are  alike,  the  rod  three-fourths  of  an  inch  long, 
set  in  an  opening  of  corresponding  length  through  the  cen- 
ter of  the  metal  disk,  is  all  that  could  be  desired  for  this  test. 
It  can  be  readily  seen  that,  if  before  one  eye  is  a  -|-i.oo  and 
before  the  other  a  +2.00,  a  serious  error  could  result  in  the 
test  for  vertical  heterophoria.  The  optical  center  of  the 
lens  is  immediately  behind  the  center  of  the  three-quarter 
inch  rod.  For  three-eighths  of  an  inch  above  and  below  the 
optical  center  of  the  lens  the  streak  of  light  can  be  seen,  so 
that,  in  the  case  supposed  above,  there  must  be  a  partial  or 


HETEROPHORIA. 


20I 


complete  correction  of  an  existing  hyperphoria,  or  there 
must  appear  an  artificial  hyperphoria  as  a  result  of  the  dif- 
ference in  prismatic  effect  of  the  lenses,  provided  the  axes 
of  vision  pass  above  or  below  the  centers  of  the  two  lenses. 
To  counteract  this  chance  for  error  to  creep  in  and  to  result 
in  bad  practice,  I  conceived  the  idea  of  covering  all  the  rod 
by  pasting  paper  over  it,  except  one-eighth  inch  of  its  center 
If  the  streak  is  seen  through 
this  small  opening,  it  must 
be  seen  through  (or  very 
near)  the  optical  center  of 
the  lens  before  that  eye ; 
and  at  the  same  time  the 
blaze  of  the  candle  must 
be  seen  through  the  optical 
center  of  the  lens  before 
the     fellow -eye.      The  Figure  a. 

chance  for  error  thus  eliminated  by  modification  of  the  Mad- 
dox  rod  (Figure  A),  this  test  may  be  resorted  to  with  a 
considerable  degree  of  confidence.  With  the  lens  or  com- 
bination of  lenses  needed  for  focal  correction,  placed  in  the 
posterior  receptacle  of  the  frames,  the  metal  disk  contain- 
ing the  rod  is  placed  in  the  anterior.  The  lighted  candle 
or  gas  jet  is  twenty  feet  from  the  patient.  The  eye  whose 
muscles  are  to  be  tested  is  always  the  one  before  which 
the  rod  is  placed.     Let  it  be  the  right  eye  first.     The  disk 


202 


HETEROPHORIA. 


«1||niiin«nfMlii'i|i<n u"trr>riiln-itrru<u»ui/ni|ruiQjnit^Dijii(jii{nW 


is  placed  vertically.  The  patient  is  asked  to  look  at  the 
candle,  which  he  sees  distinctly  with  his  left  eye;  and  at 
the  same  time  he  sees  a  streak  of  light  running  horizontally. 
The  left  eye  is  the  one  that  is  fixed.  If  there  is  vertical  or- 
thophoria, the  streak  will  occupy  Position  2  in  Figure  B; 
if  there  is  right  hyperphoria,  the  streak  will  occupy  Posi- 
tion  3   in    Figure    B ;    or  if    there  is  right  cataphoria,  the 

streak  will  occupy  Position  1 
in  Figure  B.  The  amount  of 
vertical  heterophoria  is  meas- 
ured by  that  prism  which  will 
throw  the  streak,  when  occu- 
pying Positions  1  or  3,  into 
Position  2.  When  right  hy- 
perphoria is  found,  -the  left 
eye,  when  tested  in  the  same 
Figure  B.  way,  will  show  the  same  de- 

gree of  cataphoria.  The  condition  of  the  superior  and  in- 
ferior recti  having  been  thus  determined,  the  disk  must  be 
revolved  until  the  rod  comes  to  the  horizontal,  when  the 
streak  will  become  vertical.  The  right  eye  being  first  under 
test  again,  if  there  is  horizontal  orthophoria,  the  streak  will 
be  found  in  Position  5,  Figure  C;  if  there  is  esophoria,  the 
streak  will  go  to  the  right  as  shown  by  Position  6,  Figure 
C;  or  if  there  is  exophoria,  the  streak  will  go  to  the  left, 
as   is    shown    by  Position  4,  Figure   C.     If  there   is   right 


,'Mll'll1«lll'l||rU|..||inl|I«'(|/M«|j/i,li;i./».#,it|||ui|ji1||||1ijll|,1|] 


l|li.|llii'illtP'illliil!)|n||)iir!Du|]lu  «"'«]  *iliMJlMf>lII|i«4ito/!/i 


HETEROPHORIA. 


203 


esophoria,  the  left  eye  tested  in  the  same  manner  will  show 
esophoria,  and  exophoria  where  there  was  right  exophoria. 
The  degree  of  horizontal  heterophoria^is  determined  by  that 
prism  which  will  remove  the  streak  from  Positions  4  or  6  to 
Position  5,  in  Figure  C.  The  rod  test  resorted  to  in  the 
way  described  is  trustworthy,  in  that  it  does  not  show  a 
condition  that  has  no  existence.  By  it  we  may  not  be  able 
to  judge  of  the  necessity 
for  an  operation,  if  we  are 
to  be  guided  by  the  line 
which  I  will  draw  later  be- 
tween operative  and  non- 
operative  cases.  If  in  any 
case  we  find  30  or  more  of 
hyperphoria,  or  io°  or 
more  of  esophoria  or  ex- 
ophoria, we  can  safely  con-  Figure  C. 
elude  that  the  patient  will  be  a  subject  for  operation  either 
immediately  or  remotely. 

In  further  investigation  of  the  case,  the  rod  is  laid  aside 
and  the  second  means  of  testing  is  taken  up.  The  Maddox 
double  prism,  or  better,  my  modification*  of  the  same,  is 
used.     This  is  placed  in   the    anterior  division  of  the  test 


*This  consists  of  two  separate  prisms  6°  each,  bases  toward  each  other, 
and  put  in  rim  of  same  size  as  those  containing  lenses  in  test  case,  the  line 
of  the  bases  passing  exactly  through  the  center  of  the  rim. 


204  HETEROPHORIA. 

frames,  as  was  the  rod,  and  is  so  set  as  to  double  the  can- 
dles seen  by  that  eye,  and  make  the  one  in  the  same  vertical 
plane  with  the  other.  While  this  is  being  done  the  fellow- 
eye  may  be  covered  by  an  opaque  disk.  After  the  double 
images  have  been  made  and  properly  placed,  the  fellow-eye 
is  uncovered,  when  at  once  a  third  candle  comes  into  view. 
If  there  is  orthophoria,  the  third  image  will  be  in  the  same 
vertical  plane  with  the  other  two,  and  just  halfway  between 
them.  While  in  this  method  either  eye  may  be  considered 
as  the  one  under  test,  it  is  my  custom  to  take  the  one  in 
which  there  is  the  single  image.  The  double  prism  being 
before  the  right  eye,  the  left  is  then  the  one  to  be  tested. 
The  middle  image  going  to  the  left,  there  is  left  esophoria; 
going  to  the  right,  there  is  left  exophoria ;  going  nearer  the 
lower  blaze,  there  is  left  hyperphoria;  going  nearer  to  the 
upper  blaze,  there  is  left  cataphoria.  In  the  same  manner 
the  right  eye  may  be  tested.  The  degree  of  heterophoria 
is  determined  by  the  prism  that  places  the  middle  image  in 
line  with  the  other  two,  and  equidistant  from  them.  The 
double  prism  test  readily  shows  any  compound  muscular  er- 
ror that  may  exist.  To  illustrate:  There  may  be  left  eso- 
phoria and  left  hyperphoria,  and  when  this  is  the  case  the 
middle  blaze  will  not  only  go  to  the  left  of  the  vertical  plane 
of  the  other  two,  but  it  will  also  approach  the  horizontal 
plane  of  the  lower  light.  The  rod  cannot,  at  the  same  mo- 
ment, show  the  two  conditions.     Of  the  two  tests,  I  consider 


HETEROPHORIA.  205 

the  rod  the  more  reliable,  though  often  they  both  are   at- 
tended by  like  results. 

In  continuing  the  double  prism  test,  a  card  on  which  there 
is  drawn  or  printed  a  single  horizontal  line  with  a  dot  in  its 
center,  is  held  before  the  patient  at  a  distance  of  sixteen 
inches.  After  placing  an  opaque  disk  before  one  eye — say 
the  left  one — while  the  double  prism  is  allowed  to  remain 
before  the  other,  the  card   is   elevated  or    depressed  until 


Figure  D. 


the  patient  sees  two  lines  with  equal  distinctness,  and  the 
dots  in  the  same  vertical  plane.  On  removing  the  disk  from 
before  the  other  eye  a  third  line  appears  between  the  other 
two.  If  there  is  orthophoria,  the  middle  line  will  be  equally 
distant  from  the  other  two,  and  the  three  dots  will  be  in  the 
same  vertical  plane,  as  is  shown  in  Figure  D.  If  there  is 
esophoria,  the  middle  dot  will  be  found  to  the  left  of  the  ver- 
tical plane  of  the  other  two,  as  shown  by  Figure  E;  if  exo- 
phoria,  it  will  go  to  the  right  of  this  plane,  as  is  shown  by 
Figure  F.     When  a  vertical  error  exists  it  is  shown  by  the 


206  HETEROPHORIA. 

middle  line  going  toward  the  lower  in  hyperphoria,  as  in 
Figure  G :  or  toward  the  upper  in  cataphoria,  as  in  Figure 
H.     As  in  the  distant  test,  so  in  the  near,  the  existence  of  a 


Figure  E. 


compound  error  is  shown  at  the  one  glance,  by  the  middle 
line  going  to  the  right  or  left  and  approaching  the  top  or 
bottom  line. 

In  this  near  test  with  the  double  prism,  the  same  vertical 


Figure  F. 

heterophoria  is  shown  as  was  manifested  in  the  far  test;  but 
the  degree  of  error  manifested  is  usually  a  little  more  in  the 
near  than  in  the  far  test.  If  there  is  esophoria  in  the  far 
test,  there  is  either  a  less  degree  of  esophoria,  or,  as  is  often 


HETEROPHORIA.  207 

the  case,  there  is  exophoria  in  the  near.  In  only  very  few 
cases  is  esophoria  greater  in  the  near  than  in  the  far.  More 
exophoria  is  nearly  always  shown  by  the  near  test  than  was 
brought  out  by  the  far  test.  Orthophoria  for  distance  and 
exophoria  in  the  near  is  common. 


Figure  G. 


In  both  the  near  and  the  far  test  with  the  double  prism, 
the  patient  may  see  but  two  images,  the  vertical  error  being 
so  great  that  the  middle  has  blended  with   either  the  upper 


Figure  H. 


or  the  lower  image.  The  result  is  easily  reached  by  hold- 
ing the  opaque  disk  before  first  one  eye  and  then  the  other. 
With  the  disk  before  the  eye  with  the  single  image,  if  the  two 
lights  or  two  lines  are  still  seen,  it  proves  that  the  middle  im- 
age was  blended  with  one  of  the  other  two.     By  placing  the 


2oS  HETEROPHORIA. 

disk  now  before  the  other  eye — the  one  with  the  double  im- 
age in  it — the  top  line  only  is  made  to  disappear,  showing 
hyperphoria  to  exist  in  the  fellow-eye ;  or  if  the  bottom  line 
is  the  one  to  disappear,  the  condition  is  shown  to  be  cata- 
phoria. 

The  third  in  order  is  the  strength  test.  I  rarely  apply 
this  except  to  the  superior  and  inferior  recti;  though  I  am 
more  and  more  convinced  that  it  also  has  a  real  value  when 
applied  to  the  external  recti  as  well.  For  testing  the 
strength  of  the  superior  and  inferior  recti ;  a  Maddox  double 
prism  (40  each)  is  most  convenient.  Either  eye  can  be 
taken  first.  The  patient  is  made  to  look  first  through  the 
upper  prism  at  the  candle  twenty  feet  distant,  and  it  is  noted 
whether  two  lights  or  one  are  seen;  and  if  two,  their  dis- 
tance apart.  Now  the  double  prism  is  elevated  so  that  the 
eye  before  which  it  is  held  looks  through  the  lower  prism; 
and  the  same  note  is  made  as  when  the  prism  was  in  the 
former  position.  If  the  two  images  are  the  same  distance 
apart  in  the  two  positions  of  the  prism,  it  shows  equal 
strength  on  the  part  of  these  opposing  muscles;  but  if,  when 
the  upper  part  of  the  prism  is  used,  the  two  images  are  near 
each  other,  say  one  or  two  inches  apart,  while  they  are  six 
or  more  inches  apart  when  the  lower  part  of  the  prism  is 
used,  there  is  an  excess  of  power  in  the  superior  rectus. 
The  same  test  applied  to  the  fellow-eve  would  show  an  ex- 
cess of  power  in  the  inferior  rectus.     This  test  is  confirma- 


HETEROPHORIA.  200, 

tory  of  the  two  preceding  tests,  and  much  reliance  can  be 
placed  in  it. 

As  to  the  strength  test  of  the  external  rectus,  the  follow- 
ing is  a  good  rule :  If  that  muscle  can  overcome  a  prism  of 
more  than  8°,  there  is  exophoria;  if  less  than  8°,  esophoria 
is  to  be  suspected. 

The  fourth  test  is  that  by  means  of  the  plane  deep  red 
glass,  nothing  else  being  before  the  eyes  except  the  lenses- 
correcting  focal  errors.  While  in  a  large  proportion  of 
cases  this  test  is  negative,  yet  it  is  one  most  useful,  as 
will  be  presently  shown.  The-  image  of  the  flame  (twenty 
feet  distant)  on  the  retina  of  the  eye  before  which  the  red 
glass  is  placed,  is,  of  course,  greatly  modified  as  compared 
with  the  image  in  the  fellow-eye.  If  there  is  orthophoria,, 
or  if  there  is  heterophoria  of  low  or  even  of  moderate  de- 
gree, the  images  will  be  fused  and  only  one  blaze  will  be 
seen;  but  if  there  is  heterophoria  of  high  grade,  the  images 
may  not  fuse,  a  red  light  being  seen  by  one  eye  and  a 
white  light  b}^  the  other.  The  patient  is  asked  to  fix  the 
white  blaze,  and  at  the  same  time  observe  the  position  of  the 
red  blaze,  and  the  distance  between  the  two.  Figure  I  il- 
lustrates the  result  brought  about  by  this  test.  The  bold, 
sharply  defined  candle  (7)  represents  the  white  one,  the 
pale  candles  above  (8)  and  to  the  right  (9)  of  the  other  rep- 
resent the  red  candles.  The  red  glass  being  first  before 
the  right  eye,  the  patient  at  once  says  he  sees  two  candles, 
14 


2IO 


HETEROPHORIA. 


the  red  one  being  directly  above  the  white,  and  that  they 
are  from  one  to  four  or  more  inches  apart.  This  is  positive 
evidence  of  right  cataphoria,  or,  if  the  term  is  objected  to, 
left  hyperphoria.  The  extent  of  the  deviation  is  measured 
by  that  prism  which  will  cause  the  images  to  fuse.  If  there 
is  vertical  orthophoria,  while  at  the  same  time  there  is  hori- 
zontal heterophoria  of  high  degree,  the  red  light  (9)  will 
appear  in  the  same  horizontal  plane  with  the  white  one  and 

they  will  be  from  one  to  many 
inches  apart  (in  one  of  my 
cases  they  were  thirty  inches 
apart).  If  there  is  right  eso- 
phoria,  the  red  candle  will  be 
to  the  right,  as  in  Figure  I;  if 
right  exophoria,  then  the  red 
candle  would  be  to  the  left  of 
the  white  one. 

If  a  compound  muscular  er- 
ror exists,  the  red  glass  in  suitable  cases  will  show  it  at  a 
glance.  The  head  being  perfectly  erect,  if  there  is  right 
cataphoria  and  esophoria  (the  red  glass  before  the  right 
eye),  the  red  light  will  be  above  and  to  the  right  of  the 
white,  occupying  the  position  +  in  Figure  I.  In  all  of  the 
cases  of  this  class  there  is,  without  the  interposition  of  the 
red  glass,  binocular  single  vision,  as  can  be  most  readily 
determined.      Otherwise  the  test  would  be  without  value. 


8 
7  f 

1 

4 

|                        + 
f. 

\            9  0 

j      j 
i        ■ 

\              4A 

Fisrure  I. 


HETEROPHORIA.  211 

The  fifth  test  is  never  resorted  to  when  the  fourth  (the 
red  glass  test)  results  in  diplopia.  In  some  cases,  under 
the  first  three  tests,  the  results  are  conflicting,  especially 
as  to  the  vertical  heterophoria.  To  clear  the  doubt,  if 
possible,  a  Maddox  double  prism  (40  each),  line  of  bases 
horizontal,  is  placed  before  one  eye,  while  another  double 
prism  (6°  each),  line  of  bases  vertical,  is  placed  before 
the  other  eye.  On  looking  in  the  direction  of  the  candle 
twenty  feet  distant,  four  candles  are  seen,  two  in  a  ver- 
tical plane  and  two  in  a  horizontal  plane.  If  there  is  ortho- 
phoria, these  planes  will  bisect  each  other,  and  the  four  can- 
dles will  form  a  perfect  diamond.  If  there  is  hyperphoria, 
the  horizontal  plane  will  cut  the  vertical  plane  nearer  the 
lower  candle,  sometimes  passing  through  it.  If  there  is  a 
horizontal  as  well  as  a  vertical  heterophoria,  the  right  image 
may  run  into  the  lower  one,  the  left  one  going  farther  away 
from,  but  stopping  in  the  same  horizontal  plane  with,  the 
latter.  Two  having  gone  into  one,  but  three  images  re- 
main, and  these  form  a  right-angle  triangle. 

It  must  be  confessed  that,  in  some  cases,  after  all  known 
tests  have  been  resorted  to,  there  still  remains  doubt  as  to 
what  the  true  muscular  condition  is.  In  such  cases  it  is 
best  to  do  nothing-. 

In  this  paper  I  have  not  referred  to  the  Stevens  phorome- 
ter,  one  of  the  best  if  not  the  very  best,  means  of  determining 
heterophoric  conditions.     The  chief  objection  to  it  is  its  cost. 


212  HETEROPHORIA. 

Having  thus  far  discussed  heterophoria  and  some  of  the 
tests  that  may  be  resorted  to  for  its  determination,  I  am 
ready  to  draw  a  safe  line  between  operative  and  non-operative 
cases.  On  the  operative  side  of  the  line  must  be  placed  all 
cases  in  which  the  plane  red  glass  produces  diplopia.  On 
the  non-operative  side  of  the  line  should  be  placed,  at  least 
for  a  time,  all  cases  of  heterophoria  in  which  there  is  not 
diplopia  when  the  plane  red  glass  is  before  one  eye.  Prisms, 
or  decentered  lenses,  in  position  of  rest  should  always 
be  resorted  to  primarily  in  all  cases  falling  on  the  non- 
operative  side  of  the  line.  [I  now  believe  this  teaching  to 
be  erroneous.  Prisms  and  decentered  lenses  in  position  of 
rest  make  the  strong  muscles  stronger  and  the  weak  mus- 
cles weaker,  developing  a  so-called  latent  heterophoria, 
which  should  never  be  done.  But  this  more  fully  at  end  of 
this  chapter.]  In  those  cases  in  which  the  third  theory  for 
heterophoria,  given  in  this  paper,  is  the  true  one,  nothing 
but  prisms  placed  as  above  will  ever  be  needed.  [I  still  be- 
lieve this  to  be  true,  but  these  cases  are  rare.] 

In  operating  on  cases  responding  to  the  red  glass  test,  a 
fairly  free  division  of  the  tendon  of  the  strong  muscle  must 
be  made.  One  or  more  fibers  should  be  left  above  and  be- 
low in  order  to  prevent  too  great  an  effect,  immediate  or  re- 
mote. The  miide  as  to  when  enough  is  done  short  of  a 
complete  division  of  the  tendon  is  a  fusion  of  the  red  and 
white  lights.     While  operating,  the  test  should  be  resorted 


HETEROPHORIA.  21 3 

to,  to  show  what  effect  has  been  gained  by  the  cutting  al- 
ready done.  In  no  case  should  the  red  light  be  made  to 
cross  to  the  opposite  side  of  the  white  light,  as  will  nearly  al- 
ways be  the  case  when  the  whole  tendon  has  been  severed. 
If  a  complete  tenotomy  is  done  accidentally  or  on  purpose, 
an  advancing  stitch  is  nearly  always  necessary. 

In  cases  demanding  an  operation  when  there  is  no  re- 
sponse to  the  red  glass  test,  the  division  of  the  tendon  must 
be  done  with  still  greater  care,  else  an  over-effect  will  result. 


In  addition  to  the  modifications  inclosed  in  brackets  in 
the  foregoing  paper,  I  have  omitted  a  few  paragraphs  de- 
scriptive of  the  plan  I  then  followed  of  using  prisms  in  po- 
sition of  rest,  for  the  relief  of  symptoms  dependent  on  low 
degrees  of  muscular  errors.  While  in  some  cases  this  treat- 
ment was  satisfactory,  in  the  majority  of  these  cases  the  re- 
lief was  only  temporary;  and  in  other  cases  the  prisms  were 
a  source  of  increased  annoyance  from  the  beginning.  I 
now  believe  prisms  in  position  of  rest  indicated  only  in 
cases  of  decentration  of  the  macular.  Even  in  these  cases 
the  chief  reason  for  using  prisms  is  that  they  give  to  such 
eyes  the  ability  to  obey  the  law  of  projection.  In  all  other 
cases  the  development  of  the  weak  muscles  by  graduated 
rhythmic  exercise  is  the  proper  thing  to  be  done,  when  the 
muscle  error  is  not  too  great. 


214  HETEROPHORIA. 

While  in  this  chapter  the  line  drawn  between  operative 
and  non-operative  cases  is  a  safe  one,  it  is  not  sufficient. 
Those  just  beginning  to  operate  would  do  well  to  practice 
on  the  safe  line.  While  there  are  many  cases  that,  under 
ordinary  circumstances,  have  binocular  single  vision,  in 
whom  the  red  glass  will  develop  diplopia,  there  are  many 
more  cases  of  heterophoria  sufficiently  great  to  demand  op- 
erative interference,  in  whom  the  red  glass  is  incapable  of 
bringing  about  diplopia.  All  exophoria  for  distance  should 
be  relieved  by  operations ;  all  intrinsic  esophoria  in  the 
near  should  be  corrected  by  operations;  hyperphoria  and 
cataphoria  of  2°  or  more  should  be  operated  upon.  Under 
the  exclusion  test,  should  the  eyes  reset  in  both  the  distant 
and  near  tests,  there  is  certainly  enough  muscle  error  not 
only  to  justify  but  even  demand  an  operation.  Exophoria 
in  the  near  with  orthophoria  for  distance  should  never  be 
operated  upon;  and,  a  $rio?-i,  exophoria  in  the  near  with 
esophoria  in  the  distance  should  not  be  operated  upon.  In 
the  former  case  an  operation  giving  relief  to  a  part  of  the 
exophoria  in  the  near  would  give  an  esophoria  for  distance ; 
in  the  latter  case,  the  operation  for  the  exophoria  would 
give  an  increase  of  the  esophoria.  The  proper  method  of 
dealing  with  cases  like  these  is  fully  set  forth  in  the  chapter 
on  "  Rhythmic  Exercise." 

Is  there  such  a  condition  as  latent  heterophoria?  If  so, 
is  it  good  practice  to  bring  it  out  by  prisms  in  position  of 


HETEROPHORIA.  215 

rest?     When  there  is  a  want  of  harmony  between  the  exter- 
nal and  internal  recti,  or  superior  and  inferior  recti,  one  or 
more  of  the  several  tests  will  show  it;   and  having  found  the 
error,  the  line  of  duty  is  to  combat  the   known  enemy  and 
not  add  to  its  power  by  uncovering  the  so-called  latent  force. 
The  practice  of  making  manifest  a  latent  muscle  error  has 
been  confined  almost  entirely  to   the  superior  and  inferior 
recti.     For  illustration:    On  the  first  examination  the  patient 
shows  left  hyperphoria,   *4° ;   the  second  and  third  examina- 
tions show  the  same  thing;   and   so  on  for  any  number  of 
examinations.     Imbued   with  the  idea  that  there  is  such  a 
condition   as    a  latent  hyperphoria,   the  patient  is  given    a 
prism  of  y°,  base  down,  for  left  eye,  with  instruction  to  wear 
same  continuously  for  a  few  days.     In  due  time  the  patient 
returns.     The    prism    is    removed    and    the  test  is  applied, 
with  the  gratifying  (  ? )  result  that  now  there  is  hyperpho- 
ria y±°.     The  y2°  prism  is  allowed  to  remain  before  the  left 
eye  and  a  prism  of  %° ,  base  up,  is  given  for  the  right  eye; 
and  the  patient  is  directed  to  wear  these   all  the   time,    and 
return  to  the  office  in  a  week  or  two.     Now,  with  prisms  re- 
moved, i°  of  left  hyperphoria  is  shown — y°  of  latent  has 
been   added  to  the    y°  manifest.     Increasing  the   strength 
of  the  prisms  further,   there   is   brought  into   the   manifest 
state  still  more  of  the  latent  hyperphoria;   so  that  a  patient 
who  had  primarily  only  %°  of  hyperphoria,  has  now  i%°  or 
2°,  possibly  more,  of  this  error.     The  point  must  be  finally 


2l6  HETEROPHORIA. 

reached,  however,  beyond  which  it  is  not  possible  to  un- 
cover an  additional  quantity  of  the  so-called  latent  trouble. 
This  limitation  is  due  to  one  of  two  causes,  viz.,  (i)  the 
prisms  become  so  strong  that  their  continuous  use  brings  too 
much  fatigue  to  the  stronger  muscle,  which  would  have  a 
greater  tendency  to  weaken  than  to  still  further  strengthen; 
(2)  the  actual  turning  of  the  eye,  resulting  from  the  use  of 
the  prism,  finally  reaches  a  point  backward  (toward  the 
apex  of  the  object)  that  is  equivalent  to  setting  the  insertion 
of  the  stronger  muscle  back,  while  the  weaker  muscle  finds 
its  relation  to  the  rotated  globe  equal  to  a  slight  advancement. 
The  smaller  the  difference  in  the  relative  strength  of  the  two 
muscles,  the  sooner  would  this  point  be  reached.  To  illus- 
trate: If  two  men,  the  one  being  stronger  than  the  other, 
are  to  lift  a  certain  weight  by  means  of  a  stick  beneath  it, 
it  is  plain  that  if  the  load  be  placed  in  the  middle  of  the 
stick  the  weak  man  will  have  to  lift  too  much  for  his  com- 
parative strength;  but  if  the  load  be  placed  nearer  the 
stronger  man,  the  weaker  man  can  now  lift  with  him  and 
not  be  strained  more  than  he.  The  changed  position  of  the 
globe  is  to  the  weaker  muscle  what  passing  more  than  half 
the  stick  is  to  the  weaker  man.  I  may  be  allowed  here  to 
say  parenthetically  that  there  is  another  way  to  enable  the 
weaker  man  to  lift  with  the  stronger:  develop  his  (the 
weaker  man's)  muscular  power  by  gymnastic  exercise. 
It  is  fortunate  that,  in  making  manifest  a  latent  muscular 


HETEROPHORIA.  2I1 


error,  the  practice  has  been  to  compel  the  patient  to  wear 
the  prisms  continuously,  thus  setting  a  limit  to  this  work. 
If  such  a  thing  were  attempted  by  the  proper  gymnastic  ex- 
ercise of  the  strong  muscle,  every  week  more  and  more  of 
a  supposed  latent  error  would  be  brought  out;  because  day 
after  day  the  strong  muscle  would  be  made  stronger  by  the 
exercise.  In  this  way  it  would  be  possible,  in  time,  to  aug- 
ment a  slight  degree  of  hyperphoria,  until  finally  it  would  be 
converted  into  a  hypertropia.  The  same  thing  would  hold 
true  as  to  any  of  the  extrinsic  ocular  muscles. 

I  believe  that  we  should  be  content  with  whatever  muscle 
errors  we  find  manifest;  the  smaller  the  degree  of  a  mani- 
fest error  the  happier  we  should  be.  In  no  case  should  we 
institute  a  search  for  a  hidden  error,  be  the  manifest  error 
great  or  small.  If  the  error  is  great,  an  operation  on  the 
strong  muscle  is  at  once  indicated;  if  the  error  is  small,  we 
should  strive  to  make  it  less,  day  after  day,  by  directing  our 
prismatic  power  toward  the  weak  muscle  in  such  a  way  as 
to  develop  its  strength.  To  accomplish  this  by  means  of 
rhythmic    exercise,    resorting  to  it    intermittingly,    will    be 

easv. 

I  will  close  this  chapter  by  giving  the  technique  of  what  I 
conceive  to  be  the  proper  method  of  operating  for  the  cure 
of  heterophoria.  In  no  case  of  any  of  the  several  forms  of 
heterophoria  should  a  complete  tenotomy  be  done ;  in  no 
case  should  a  second  operation  be  done  on  any  one  muscle. 


2l8  HETEROPHORIA : 

When  the  error  to  be  relieved  is  at  all  great,  the  operative 
effect  should  be  divided  between  the  two  corresponding 
muscles ;  but  the  aim  should  always  be  to  fall  short  of  a  full 
correction  rather  than  incur  the  risk  of  an  over-effect, 
leaving  a  small  part  of  the  old  error  to  be  corrected  by 
rhythmic  exercise.  After  the  first  operation  the  second  one 
should  be  delayed  at  least  one  month;  and  another  month 
should  elapse  before  resorting  to  exercise  for  the  relief  of 
any  remaining  error.  Knowing  that  a  very  small  division 
of  the  center  of  the  tendon  will  effect  but  little,  if  any, 
change  in  the  muscular  error,  the  operation  should  be  under- 
taken with  the  understanding  that  it  must  be  made  more  or 
less  extensive;  the  greater  the  error  the  more  nearly  must 
the  division  approach  the  margins  of  the  tendon.  The  ef- 
fect of  a  partial  tenotomy  depends  not  solely  on  the  extent 
of  the  division  of  the  tendon,  but  also  on  the  amount  of 
retraction  of  the  divided  portion.  The  retraction  can  be 
very  little  if  the  cutting  of  the  capsule  of  Tenon  is  not  coex- 
tensive with  the  cutting  of  the  tendon. 

The  Operation  of  Partial  Tenotomy, 

as  done  by  myself,  is  performed  under  cocaine  anaesthesia, 
with  the  following  instruments:  Stop  speculum,  ordinary 
fixation  forceps,  and  Stevens's  scissors  and  hook.  If  the 
condition  is  hyperphoria,  I  operate  first  on  the  superior  rec- 
tus of  the  hyperphoric  eye.     Asking  the  patient  to  look  to- 


HETEROPHORIA.  2IO, 

ward  the  feet,  I  seize  with  the  fixation  forceps  the  conjunc- 
tiva, capsule,  and  tendon,  at  the  point  of  insertion  of  the  lat- 
ter. Between  the  forceps  and  sclera  I  make  a  small  cut 
with  the  scissors  through  all  the  structures  held  by  the  for- 
ceps, making  as  small  a  cut  as  possible,  which  is  usually 
one-tenth  to  one-eighth  of  an  inch.  Laying  the  scissors 
down,  but  still  holding  on  with  the  forceps,  I  take  the  hook, 
and,  passing  it  through  the  opening,  which  I  intended  should 
be  in  the  center  of  the  tendon,  test  the  strength  and  ex- 
tent of  the  undivided  fibers  in  both  directions.  If  convinced 
that  there  are  many  uncut  fibers  on  both  sides  of  the  open- 
ing, I  lay  down  the  hook  and  take  up  the  scissors  again. 
Without  enlarging  the  conjunctival  opening,  I  pass  the 
closed  scissors  in,  but  immediately  open  them,  passing  one 
blade  behind  the  tendon  and  the  other  in  front  of  the  cap- 
sule. Having  made  as  many  snips  as  I  deem  safe  in  that 
direction,  I  withdraw  the  scissors  and  test  with  the  hook. 
Having  decided  that  I  have  gone  as  far  in  that  direction  as 
is  safe,  without  the  hook  as  a  guide,  I  again  take  the  scis- 
sors, while  still  holding  on  with  the  forceps,  and  divide  the 
capsule  and  tendon  in  the  same  careful  manner,  in  the 
other  direction.  I  now  lay  the  forceps  down,  and,  with 
hook  in  hand,  test  the  strength  and  extent  of  undivided 
fibers  in  each  direction.  If  more  is  needed,  it  is  done  under 
the  guidance  of  the  hcok.  With  every  snip  of  the  scissors 
both  capsule  and  tendon  are  divided,   and  after  each  snip 


2  20  HETEROPHORIA. 

the  hook  is  made  to  tell  if  more  must  be  done.  The  habit 
of  resorting  to  one  or  more  of  the  muscle  tests  as  the  oper- 
ation proceeds  is  unnecessary,  and  may  be  misleading.  In 
a  case  where  there  is  diplopia  with  the  red  glass,  I  would 
fuse,  or  nearly  fuse,  the  two  images,  if  this  could  be  done 
short  of  a  complete  division  of  the  tendon.  To  know  that 
this  has  been  accomplished,  the  red  glass  test  must  be  re- 
sorted to.  When  the  fusion  is  made  to  take  place  there  is 
enough  of  the  condition  left  to  demand  a  subsequent  opera- 
tion on  the  corresponding  muscle.  Necessarily  some  bleed- 
ing attends  these  operations.  So  as  to  give  a  clear  field  for 
operating,  the  blood  must  be  removed  by  means  of  pledgets 
of  previously  prepared  absorbent  cotton.  In  the  use  of 
these  pledgets  care  must  be  exercised  that  the  cornea  be 
not  touched,  since  the  slightest  touch  might  remove  its 
epithelium,  which  has  been  so  acted  on  by  the  cocaine  as  to 
make  this  accident  easy.  If  the  patient  should  suffer  after 
a  partial  tenotomy,  it  is  usually  due  to  accidental  corneal 
abrasion.  The  after-treatment  I  usually  prescribe  consists 
of  morphia  sulph.,  gr.  i. ;  acid  boracic,  gr.  x. ;  aqua  distil., 
fsi.  Two  drops  in  eye,  three  or  four  times  a  day.  No 
bandage  or  protection  of  any  kind  need  be  applied.  While 
the  patient  should  not  be  kept  in  his  room,  he  certainly 
should  not  be  allowed  to  use  his  eyes  in  continuous  near 
work  for  at  least  a  few  days. 

At  intervals  of  a  few  days,  when  convenient  to  the  pa- 


HETEROPHORIA.  221 

tient,  the  tests  should  be  applied  and  results  should  be  not- 
ed. If,  at  the  end  of  four  weeks,  there  should  be  enough 
hyperphoria  remaining  to  indicate  a  second  operation,  a 
partial  tenotomy  of  the  inferior  rectus  of  the  other  eye 
should  be  made,  in  the  same  careful  manner  as  was  the  op- 
eration on  the  tendon  of  the  superior  rectus  at  the  first  oper- 
ation. The  one  muscle  is  as  easily  operated  on  as  the  oth- 
er. The  hyperphoria  must  be  great  that  cannot  be  almost 
completely  cured  by  these  two  operations.  Great  care 
must  be  exercised  in  the  second  operation,  lest  an  over-ef- 
fect may  follow. 

Varying  the  position  of  the  eye,  the  technique  of  the  op- 
eration on  the  internal  recti  in  a  case  of  esophoria,  and  on 
the  external  recti  in  exophoria,  is  exactly  the  same  as  that 
already  given  for  the  superior  and  inferior  recti  in  a  case  of 
hyperphoria.  Between  operations  I  allow  my  patients  to  re- 
turn home,  unless  they  reside  at  too  great  a  distance. 

Not  infrequently. an  esophoria  or  an  exophoria  is  so  great 
in  degree  that  a  partial  tenotomy  of  the  two  corresponding 
muscles,  although  the  tendons  may  be  almost  completely  di- 
vided, does  not  reduce  the  error  within  the  range  of  possi- 
bility of  completing  the  cure  by  gymnastic  exercise  of  the 
weaker  muscles.  In  such  cases  I  shorten  one  or  both  of  the 
weaker  muscles,  after  the  method  set  forth  in  Part  III.  of 
this  book.  Since  this  operation  must  necessarily  be  attend- 
ed by  pain  and  inconvenience,  I  prefer  doing  what  remains 


222  HETEROPHORIA. 

to  be  done  on  one  muscle.  If  it  was  no  more  annoyance  to 
a  patient  than  a  partial  tenotomy,  I  would  prefer  dividing 
the  effect  sought  by  shortening,  between  the  two  muscles. 

Whether  one  or  several  of  these  operations  is  to  be  done, 
I  always  aim  to  fall  short  of  a  full  correction,  rather  than  in- 
cur the  risk  of  an  over-effect.  We  may  never  expect  to 
have  means  of  guaging  to  a  nicety  the  effect  of  these  oper- 
ations. It  is  well,  therefore,  that  we  can  call  to  our  aid,  in 
completing  a  cure  of  muscle  errors,  such  a  simple  and  so 
entirely  harmless  a  method  as  rhythmic  gymnastic  exercise 
of  weak  muscles. 


CHAPTER  II. 

THE  NECESSITY  FOR  COMPLETE  SUSPENSION  OF 
ACCOMMODATION  BY  MYDRIATICS  IN  THE  AD- 
JUSTMENT OF  GLASSES. 

If  the  accommodation  could  be  suspended  instantaneous- 
ly, and  then,  after  the  work  of  refraction  has  been  accom- 
plished, could  be  as  speedily  restored  to  the  normal,  who 
and  where  is  the  oculist  who  would  not  exercise  such  magic- 
al power  in  all  his  cases  of  refraction  ?  If  the  exercise  of 
this  supposed  magical  power  would  be  justifiable,  then  there 
must  be  some  strong  reasons  for  using  the  means  really  at 
our  command  for  putting  at  rest  the  ciliary  muscle  when  a 
focal  error,  whatever  may  be  its  nature,  is  to  be  corrected. 
It  is  the  object  of  this  paper  to  give  the  reasons  that  not 
only  justify,  but  actually  demand,  the  use  of  the  mydriatic 
in  refractive  work. 

For  the  sake  of  fairness,  the  reasons  against  the  use  of 
the  mydriatic,  except  in  rare  and  remote  instances,  will  be 

given : 

i.  It  interferes  with  the  business  of  the  patient.  This  of 
course  applies  to  the  banker  and  the  butcher,  to  the  lady 
whose  business  is  to  read  the  latest  novel,  and  to  the  girl 

(223) 


224        NECESSITY   FOR   SUSPENSION   OF   ACCOMMODATION, 

who  has  to  sew  for  her  daily  living — in  fact,  about  all  of  our 
patients  need  the  eyes  for  near  use  at  least  a  part  of  every 
day. 

2.  The  general  inconvenience  to  the  patient,  leaving  out 
the  question  of  using  the  eyes  in  near  work.  The  pupil  be- 
ing dilated,  a  flood  of  light  enters  the  eye  and  the  patient  is 
annoyed  by  the  dazzling  it  produces;  and,  except  in  my- 
opia, there  is  always  an  attendant  dimness  of  both  distant 
and  near  vision,  greater  or  less  in  degree.  In  rare  instances 
there  is  a  slight  toxic  effect. 

3.  The  chromatic  and  spherical  aberration  resulting  from 
the  dilation  of  the  pupils  is  not  only  annoying  to  the  patient,, 
but  is  otherwise  undesirable. 

4.  The  operator  is  delayed,  and  his  time  is,  of  course, 
valuable. 

5.  There  is  the  alleged  danger  that,  in  old  people,  the 
mydriatic  may  excite  the  glaucomatous  state. 

6.  Glasses  prescribed  without  a  mydriatic  are  often  com- 
fortable. 

7.  One  other  reason  which  has  been  advocated,  but  which 
is  absurd  on  its  face,  is  that  the  error,  especially  if  it  be  as- 
tigmatism, cannot  be  as  thoroughly  corrected  when  the  eye 
is  under  the  influence  of  a  mydriatic  as  when  not. 

In  presenting  the  numerous  reasons  for  the  use  of  the 
mydriatic  in  the  work  of  refraction,  all  the  reasons  above 
given  against  its  use  will  be  met. 


NECESSITY   FOR   SUSPENSION  OF   ACCOMMODATION.       225 

While  in  some  cases  glasses  may  be  prescribed  simply  to 
sharpen  vision,  it  must  be  confessed  that  the  greater  number 
of  cases  coming  under  the  observation  of  the  oculist  are 
persons  who  suffer  because  of  strain.  This  leads  us  to  in- 
quire :  What  is  eye  strain  ?  A  clear  understanding  of  what 
the  answer  to  this  question  should  be  will  go  far  toward  set- 
tling the  question  of  the  proper  line  of  practice  intended  for 
its  relief.     None  will  controvert  the  statement  that 

Eye  Strain  Is  Muscle  Strain; 
and  that  the  muscles  concerned  in  the  visual  act  are :  First, 
those  regulating  the  quantity  of  light  admitted  into  the  eye 
and  the  direction  of  its  rays  (these  are  the  two  sets  of 
fibers  in  the  iris  and  the  ciliary  muscle);  secondly,  the  ex- 
trinsic muscles — the  recti  and  the  obliqui — which  are  con- 
cerned in  directing  the  visual  axes  and  in  keeping  the  nat- 
urally vertical  meridians  of  the  corneas  so  related  that  im- 
ages may  fall  on  corresponding  parts  of  the  two  retinas. 
Muscular  action  is  not  muscle  strain,  unless  the  action  is  ei- 
ther too  prolonged  or  too  great  for  the  inherent  power  of 
the  muscle.  Some,  by  their  teaching,  would  show  that  only 
the  ciliary  muscle  is  susceptible  of  strain ;  and  that  ciliary 
strain  alone  is  capable  of  bringing  into  existence  that  long 
train  of  nervous  phenomena  with  which  the  oculist  and,  of 
late  years,  the  neurologist  are  so  well   acquainted.     There 

are  others  who  are  accused  of  believing  and  teaching  that 
15 


226       NECESSITY   FOR   SUSPENSION  OF  ACCOMMODATION. 

the  extrinsic  muscles  are  alone  susceptible  of  that  fatigue 
which  brings  discomfort,  in  varied  forms,  to  our  patients. 
There  are  not  a  few,  however,  whose  practice  is  governed 
by  the  sounder  doctrine  that  both  the  intrinsic  and  extrinsic 
eye  muscles  may  be  put  to  the  necessity  of  doing  more  work 
than  their  strength  will  bear;  and  that  the  consequent  strain, 
whether  in  the  one  set  or  in  the  other,  or  in  both  at  the  same 
time,  will  develop  headache,  vertigo,  confusion  of  thought, 
and  a  host  of  other  phenomena.  While  glasses,  prescribed 
for  the  correction  of  focal  errors,  were  once  thought  capa- 
ble of  curing  all  symptoms  depending  on  eye  strain,  the 
time  is  now  when  no  such  claim  can  be  sustained.  Lenses 
that  give  a  perfect  correction  of  existing  focal  errors  may  in 
some  instances  augment,  rather  than  allay,  the  suffering  due 
to  eye  strain.  Such  patients  would  be  better  without  lenses 
until  the  chief  cause  of  suffering,  in  the  individual  case,  has 
been  found  and,  by  the  proper  treatment,  cured. 

But  I  am  not  the  one  to  cry  out  against  the  prescribing  of 
glasses.  My  wearing  lenses  is  sufficient  evidence  of  my  re- 
gard for,  and  my  appreciation  of,  them.  Properly  deter- 
mined, scientifically  prescribed,  and  correctly  worn,  they  do 
only  good.  But  in  prescribing  glasses  we  must  take  into 
consideration  both  the  focal  error  and  the  muscular  adjust- 
ment, particularly  the  adjustment  of  the  internal  and  exter- 
nal recti.  Since  glasses  can  do  more  than  relieve  ciliary 
strain — they  can,  if  properly  selected,  relieve  strain  of  the  in- 


NECESSITY   FOR   SUSPENSION   OF   ACCOMMODATION.       227 

ternal  and  external  recti,  independent  of  prismatic  effect;* 
also  strain  of  the  oblique  muscles  in  cases  of  oblique  astig- 
matism— they  should  be  scientifically  prescribed,  after  a 
most  painstaking  study  of  the  focal  error  and  the  muscular 
adjustment. 

For  the  present,  fixing  our  attention  on  focal  errors,  we 
find  that  there  are  these:  myopia,  hypermetropia,  and  the 
several  kinds  of  astigmatism.  In  emmetropic  eyes  there  is 
no  strain,  in  the  proper  sense,  when  used  in  moderation. 

In  simple  myopia  of  3  D.  or  more,  the  ciliar}^  muscle  is 
never  called  into  action,  and  therefore  can  never  be  strained. 
If  such  eyes  give  annoyance,  other  than  dimness  of  distant 
vision,  the  cause  must  be  sought,  and  will  be  found,  in  the 
relationship  of  the  extrinsic  muscles. 

In  simple  hypermetropia  the  ciliary  muscle,  during  wak- 
ing hours,  is  ever  acting  until  quieted  by  age.  Any  action 
of  the  ciliary  muscle  for  sharpening  distant  vision  is  strain ; 
and  in  such  eyes  overaction  (strain)  is  necessary  in  order  to 
good  near  vision.  In  some  of  these  cases  the  ciliary  muscle 
is  hyperdeveloped ;  the  center  controlling  it  has  an  abundant 
supply  of  nerve  force ;  and  there  are  no  symptoms  resulting 
from  the  strain.  Other  hypermetropes  are  not  so  fortunate- 
ly constituted ;  and  the  ciliary  strain  caused  by  the  refract- 
ive error  is  felt  in  some  form  or  other. 

In  astigmatism,  of  whatever  kind,  with  the  principal  me- 
*See  Ophthalmic  Record,  Vol.  II.,  No.  n. 


228        NECESSITY   FOR   SUSPENSION   OF  ACCOMMODATION. 

ridians  in  the  vertical  and  horizontal,  or,  if  oblique,  the  ob- 
liquity being  in  the  same  direction  and  at  the  same  angle  in 
the  two  eyes,  the  astigmatic  refraction  also  being  equal  in  the 
two  eyes,  there  is  ciliary  strain  directed  against  this  refract- 
ive error.  As  to  the  character  of  the  effort  made  by  the 
ciliary  muscle  there  is  some  difference  of  opinion.  What- 
ever may  be  the  nature  of  this  strain,  it  is  capable  of  cor- 
recting wholly  only  the  lower  degrees  of  astigmatism,  and 
only  a  small  part  of  the  higher  degrees  of  this  error;  but 
that  the  effort  is  being  continually  made,  for  distant  and 
near  vision,  in  cases  of  hypermetropic  and  mixed  astigma- 
tism, also  in  myopic  astigmatism,  when  near  vision  is  at- 
tempted, there  can  be  no  doubt.  This  effort  is  strain  if  the 
action  is  equal  and  simultaneous  in  all  parts,  holding  the 
focal  interval  on  the  retina,  or  adjusting  the  rays  of  first  one 
principal  meridian  and  then  those  of  the  other,  as  vertical 
or  horizontal  lines  may  be  viewed ;  it  is  strain  if  the  ciliary 
muscle  acts,  as  described  by  Martin,  in  sections,  the  one  op- 
posite the  other,  thus,  by  altering  curvature,  developing  a 
lenticular  astigmatism  correcting  in  whole  or  in  part  the 
corneal;  it  is  also  strain  if  the  longitudinal  fibers  of  Bow- 
man are  alone  concerned  in  the  effort  of  correcting  the  as- 
tigmatism, by  tilting  the  lens  on  an  axis  in  a  plane  with  the 
corneal  meridian  of  greatest  refraction,  thus  producing  a 
lenticular  astigmatism  counteracting  to  some  extent  the  cor- 
neal.    In  oblique  astigmatism,  as  usually  encountered,  there 


NECESSITY   FOR   SUSPENSION   OF   ACCOMMODATION.        229 

is  a  demonstrable  necessity  for  action  (strain)  on  the  part  of 
the  obliques,*  which  in  these  cases  is  a  factor  added  to  the 
ciliary  strain  excited  by  the  astigmatism.  The  strain  caused 
by  astigmatism  is  nearly  always  a  source  of  annoyance  to 
the  patient,  and  should,  in  all  cases,  be  fully  corrected,  re- 
gardless of  any  and  all  other  conditions. 

Ciliary  strain  is  an  effort  on  the  part  of  the  ciliary  muscle 
to  increase  the  refractive  power  of  the  lens,  as  in  hyperme- 
tropia,  or  to  render  it  astigmatic  by  tilting  or  otherwise,  for 
the  correction  of  a  corneal  astigmatism.  This  action,  or 
these  actions,  of  the  ciliary  muscle  is,  from  necessity, 
brought  into  existence  in  very  early  life,  and  because  of 
daily  repetition  becomes  a  fixed  habit  of  the  muscle — a  hab- 
it whose  existence  continues,  in  nearly  all  cases,  for  a  time 
after  the  cause  for  it  has  been  taken  away  by  properly  ad- 
justed lenses.  If  this  is  true,  who  knows  that  his  work  has 
been  correctly  done  when  he  undertakes  the  correction  of  a 
refractive  error,  while  the  ciliary  muscle  is  allowed  to  con- 
tinue at  its  old  work?  That  glasses  thus  fitted  often  (for  a 
time)  give  satisfaction  is  but  a  verification  of  the  old  adage 
that  "  guess  work  is  as  good  as  any  when  it  hits." 

How  often  do  we  find  ourselves  declaring,  what  is  a  truth, 
that  ophthalmology  is  more  nearly  a  pure  science  than  any 
other  department  of  medicine?  And  is  not  this  true  mainly 
because  of  our  perfect  knowledge  of  the  refraction  of  the 

*See  Ophthalmic  Record,  Vol.  I.,  No.  1. 


23O        NECESSITY  FOR   SUSPENSION   OF  ACCOMMODATION. 

eye  and  the  conditions  that  result  from  errors  of  refraction  ? 
If  there  were  no  modifying  conditions,  nothing  could  be 
more  scientific  than  the  full  correction  of  errors  of  refrac- 
tion, which  could  not  be  done  accurately  without  first  put- 
ting at  rest  the  self-correcting  power,  the  ciliary  muscle. 
Since  these  modifying  conditions  are  known  and  can  be  re- 
moved, it  is  the  plain  duty  of  every  oculist  to  determine,  by 
a  most  thorough  and  painstaking  examination,  under  the 
only  favorable  condition,  suspension  of  accommodation, 
what  the  refractive  errors  are,  even  though  because  of  the 
existence  of  some  known  muscle  error,  he  might  know  that 
it  would  not  be  proper  to  give  fully  correcting  lenses  at  that 
time ;  for,  having  cured  the  muscle  error,  his  record  would 
enable  him  later  to  give  the  full  focal  correction.  There  is 
no  condition  of  the  extrinsic  muscles  which  would  be  dis- 
turbed by  a  full  correction  of  any  astigmatic  error;  there  is 
no  astigmatic  error  which  may  not  be  partially  concealed  by 
ciliary  strain. 

In  the  work  of  refraction  how  fortunate  for  science  and 
practice,  for  patient  and  practitioner,  that  we  have  at  our 
command 

Mydriatics, 

whose  effect  is  to  temporarily  suspend  the  self-adjusting 
power  of  the  faulty  eye,  during  which  period  artificial  cor- 
recting means  may  be  accurately  determined ! 


NECESSITY   FOR   SUSPENSION   OF  ACCOMMODATION.        23 1 

While  a  mydriatic  does  not  in  the  least  interfere  with  any 
of  our  objective  methods  of  examination,  it  gives  greater  ac- 
curacy to  most  of  these.     All  must  confess  that  the 

Ophthalmoscope 
can  measure  more  correctly  the  refractive  error  of  an  eye, 
when  under  the  influence  of  a  mydriatic,  than  when  it  is 
not.  The  man  most  skilled  in  estimating  the  refraction  of 
eyes  by  means  of  the  ophthalmoscope  must  confess  that  it 
took  both  time  and  practice  to  enable  him  to  voluntarily  sus- 
pend his  accommodation,  with  his  eye  on  the  dark  side  of 
the  instrument;  then  how  can  he  expect  the  patient,  whose 
eye  is  on  the  light  side  of  the  instrument,  to  learn  in  a  min- 
ute to  suspend  an  involuntary  power — one  that  is  being  stim- 
ulated into  activity  by  the  light  that  is  thrown  on  the  retina? 
When  there  is  forced  suspension  of  accommodation  (by  a 
mydriatic)  in  the  patient's  eye,  and  acquired  suspension  of 
accommodation  (by  practice)  in  the  observer's  eye,  then 
there  can  be  some  degree  of  accuracy  in  the  measurements 
of  the  ophthalmoscope;  otherwise  there  cannot  be. 
The  valuable  objective  examination  of 

Skiascopy 
could  not  be  so  well  made,  nor  could  the  results  be  so  accu- 
rate, if  done  when  the  eye  is  "uninfluenced  by  a  mydriatic. 
Properly  practiced,  under  favorable  conditions,  skiascopy, 
in  addition  to  detecting  and  measuring  ir^opia  and  hyper- 


232        NECESSITY   FOR   SUSPENSION   OF  ACCOMMODATION. 

metropia,  shows  quickly  the  existence  of  astigmatism,  the 
kind  and  quantity,  and,  approximately,  the  location  of  the 
principal  meridians.  A  method  capable  of  doing  so  much 
should  not  be  interfered  with  by  an  active  ciliary  muscle 
and  a  contracted  pupil. 

When  we  come  to  the  method  of 

Ophthalmometry 
we  find  that  an  active  accommodation  neither  hinders  nor 
helps.  Since  the  ophthalmometer  deals  only  with  the  cor- 
nea, we  know  that  its  findings  must  be  the  same  both  with 
and  without  a  mydriatic,  for  a  mydriatic  can  effect  no 
change  in  either  the  corneal  curvature  or  the  corneal  reflec- 
tion. If  no  effort  on  the  inside  of  the  eye  were  ever  made 
for  the  correction  of  corneal  refractive  errors,  as  is  true  in 
the  aphakial  eye,  and  all  errors  of  refraction  existed  in  the 
cornea  alone,  we  would  then  have  in  the  ophthalmometer 
an  instrument  infallible  in  its  findings,  and  the  mydriatic 
could  be  sent  into  "innocuous  desuetude."  Although  cil- 
iary action  prevents  our  relying  implicitly  on  the  ophthal- 
mometer, it  is  nevertheless  a  great  aid  in  refractive  work. 
Those  who  bought  this  instrument  and  then  consigned  it  to 
the  attic,  if  they  will  only  bring  it  down  again  and  cultivate 
its  acquaintance  a  little  more  closely,  will  find  in  it  a 
worthy  friend.  Those  whose  enthusiasm  has  led  them  to 
trust  this  instrument  implicitly  will,  on  more  careful  study, 


NECESSITY    FOR   SUSPENSION    OF   ACCOMMODATION.        233 

find  themselves  victims  of  misplaced  confidence,  for  the 
reason  already  given  fn  this  paper.  The  great  sin  for  which 
the  ophthalmometer  will  have  to  account  is  that  its  introduc- 
tion led  to  a  vigorous  renewal  of  the  effort  to  discard  the 
mydriatic  in  the  work  of  refraction. 

If  the  mydriatic  is  an  aid  in  objective  examinations,  and 
ouo-ht  not  to  be  dispensed  with,  it  is  still  more  essential  when 
the  subjective  methods  are  to  be  resorted  to,  as  they  must 
be  if  we  aim  at  accuracy  in  our  work. 

In  our  subjective  tests  there  are  causes  for  error  other 
than  activity  of  the  accommodative  muscle,  but  unfortunate- 
ly none  of  them  are  so  easily  removed  as  the  latter.  For 
the  stupidity  of  the  patient  under  examination  there  is  no 
perfect  remedy;  for  the  carelessness  and  haste  of  the  oper- 
ator there  is  a  cure  in  the  combination  of  knowledge  of  the 
conditions  under  study  and  a  determination  to  do  the  best 
possible  under  the  circumstances. 

When  we  resort  to  the  use  of  the 

Lenses  of  the  Test  Case 
our  aim  is  to  prove  the  "  findings"  of  our  objective  tests. 
If  the  fixed  habit  of  strain  is  not  suspended  by  a  mydriatic, 
though  we  labor  long  and  earnestly,  we  can  never  be  certain 
that  what  we  have  done  is  absolutely  correct.  No  one  has 
ever  yet  learned  the  art  of  coaxing  the  ciliary  muscle  into  a 
state  of  rest.     When  capable  of  acting,  it  is  always  trying  to 


234        NECESSITY   FOR   SUSPENSION   OF   ACCOMMODATION. 

correct  the  error  which  your  lenses  are  searching  out. 
This  subjective  test,  when  unopposed  by  ciliary  power,  is 
soon  satisfactorily  ended. 

If  the  need  of  a  sphero-cylinder  has  been  determined,  and 
yet  there  is  a  "  modicum  of  doubt "  as  to  whether  the  spher- 
ical part  should  be  diminished  and  the  cylindrical  increased 
in  strength,  or  vice  versa,  the  confirmatory  agency  is  the 

Jackson  Sphero-cylinder, 

the  use  of  which  can  be  depended  on  only  when  there  is 
suspension  of  the  accommodation. 

If  a  perfect  knowledge  of  the  full  error  of  refraction  in 
every  case  is  necessary,  and  this  knowledge  can  be  attained 
only  by  the  suspension  of  the  accommodation,  then  the 
reasons  against  the  use  of  the  mydriatic  can  be  easily  dis- 
posed of. 

As  to  the  interference  with  the  business  of  the  patient, 
superinduced  by  the  mydriatic:  He  comes  to  the  oculist 
because  of  the  fact  that  his  eye-strain  interferes  with  his 
business  in  one  way  or  another.  Relief  is  what  he  needs  and 
what  he  should  have — relief  in  the  fullest  sense  of  the  word 
— not  present  relief  only,  but  relief  for  the  future  as  well. 
When  told  that  his  trouble  is  due  to  eye-strain,  he  naturally 
infers  that  if  the  cause  of  that  strain  is  removed  freedom 
from  trouble  would  follow.  He  comes,  possibly,  from  a 
great  distance,   and,  though  his  business  may  need  him  at 


NECESSITY   FOR   SUSPENSION   OF   ACCOMMODATION.       235 

home,  he  is  off  seeking  comfort,  worth  more  to  him  than 
gold.  He  is  a  willing  subject,  and  complains  at  nothing 
that  is  needful  to  be  done.  He  is  a  young  man — old  men 
may  suffer  with  eye  symptoms  brought  on  by  strain  of  the 
extrinsic  muscles,  but  not  from  ciliary  strain — and  his  ac- 
commodation is  active.  This  must  be  suspended  if  the  full 
error  is  to  be  known.  If  he  is  left  to  choose,  after  a  fair  state- 
ment of  his  case  has  been  made,  he  will  agree  to  the  loss  of 
time  that  must  follow  the  use  of  the  mydriatic,  for  he  wants 
the  work  done  correctly.  Methods  and  means  that  are  cor- 
rect for  patients  at  a  distance  are  correct  for  home  people. 
As  to  the  amount  of  interference  with  business,  the  differ- 
ence is  decidedly  in  the  favor  of  the  home  man.  Besides, 
the  business  man,  being  a  sensible  man,  will  not  complain  at 
loss  of  time  necessary  in  order  that  relief  may  come,  for  he 
remembers  how  his  troubles  have,  at  times,  incapacitated 
him  for  effective  work.  There  are  few  men  whose  work  in 
bank,  store,  or  elsewhere,  cannot  be  done,  for  a  reasonable 
time,  by  a  substitute.  What  is  true  of  the  man  of  business 
is  true  of  all  patients,  lawyers,  doctors,  school  teachers, 
artists,  sewing  girls,  etc.  But  the  necessary  loss  of  time  from 
the  proper  use  of  a  reliable  mydriatic  need  not  exceed 
twenty-four  to  forty-eight  hours.  If  it  were  necessary,  the 
patient  might  be  sent  at  once  from  the  doctor's  office  to 
the  counting  room,   or  wherever  his  duties  might  call  him. 


236       NECESSITY   FOR   SUSPENSION   OF   ACCOMMODATION. 

Of  course  near  seeing  so  quickly  done  would  have  to  be 
effected  by  means  of  a  temporary  pair  of  lenses. 

The  mydriatic  whose  power  is  effective  and  yet,  as  com- 
pared with  atropine,  evanescent,  is  the  one  that  should  be 
chosen.  There  are  few  ciliary  muscles  that  will  not  respond 
to  a  solution  of  hydrobromate  of  homatropine  of  the  strength 
of  one-third  grain  to  twenty  drops  of  water,  ten  drops  of 
which,  drop  by  drop  every  five  minutes,  should  be  put  in 
each  eye.  In  ten  minutes  after  the  last  instillation  the  study 
of  the  refraction  can  be  confidently  commenced.  The  work 
completed  by  both  subjective  and  objective  tests,  within  an 
hour  and  a  half  all  told,  a  few  drops  of  a  1-500  solution  of 
eserine  may  be  used,  the  same  to  be  repeated  the  next  morn- 
ing early.  The  patient  may  then  be  sent  about  his  business. 
By  the  next  morning  the  effect  of  the  mydriatic  is  entirely 
gone. 

As  to  the  general  inconvenience  to  the  patient:  This  can 
be  readily  borne,  or  modified  by  smoked  glasses,  etc.  Sys- 
temic effects  are  rare,  and  can  be  combated  by  appropri- 
ate remedies — brandy  and  morphia. 

As  to  loss  of  time  to  the  operator:  This  is  a  myth. 
While  the  muscle  test  and  the  correction  of  the  refractive 
errors  must  be  done  by  the  operator,  he  can  safely  commit 
the  use  of  the  mydriatic  to  the  office  girl,  whose  time  is  not 
so  valuable  as  his  own.  This  method,  too,  is  restful  both  to 
the  doctor  and  the  patient;   for  the  muscle  tests  should  al- 


NECESSITY   FOR    SUSPENSION   OF  ACCOMMODATION.        237 

ways  be  made  when  the  eyes  are  uninfluenced  by  a  mydri- 
atic. After  the  eyes  are  brought  under  the  influence  of  the 
mydriatic,  the  subjective  and  objective  examinations  of  the 
focal  errors  are  soon  over,  and  the  patient  does  not  have  to  be 
reexamined  on  the  next  day,  nor  at  any  other  time,  as  a  rule. 
As  to  the  objection  that  the  mydriatic  may  increase  the 
tension  to  the  point  of  exciting  an  attack  of  glaucoma: 
This  objection  can  weigh  but  little  when  we  consider  that 
this  exists  only  in  persons  beyond  middle  life ;  and  that  in 
these  patients  the  ciliary  muscle  has  lost  more  or  less  of  its 
power,  and  a  weak  mydriatic  serves  to  completely  suspend 
what  remains.  In  these  cases,  especially  if  the  patients  are 
bevond  fifty-five  years,  the  prime  object  is  not  to  act  on  the 
ciliary  muscle,  but  to  dilate  the  pupil,  in  order  that  a  thor- 
ough examination  of  the  fundus  may  be  made  for  the  detec- 
tion of  central  choroiditis,  so  common  in  old  people ;  also 
that  the  periphery  of  the  lens  may  be  examined  for  begin- 
ning opacities.  When  these  conditions  are  detected  early, 
as  is  well  known,  proper  therapeutic  means  may  check  their 
progress,  and  make  it  possible  for  the  patient  to  have  com- 
fortable vision  during  the  remainder  of  life.  Through  the 
small  pupil  of  the  old,  these  changes  could  not  be  readily 
detected.  After  the  proper  glasses  have  been  determined, 
and  the  fundus  and  lens  have  been  thoroughly  investigated, 
the  mvotic  should  never  be  omitted  if  the  patient  is  beyond 
middle  life. 


238       NECESSITY   FOR   SUSPENSION  OF   ACCOMMODATION. 

While  advocating  the  complete  suspension  of  the  accom- 
modation, that  full  knowledge  of  the  refractive  errors  may 
be  attained,  and  made  a  matter  of  record,  I  would  not  be 
understood  as  advocating  that  the  myopic  and  the  hyper- 
metropic refraction  should  always  be  fully  corrected  in 
every  patient,  at  the  beginning.  On  the  contrary,  in  the 
light  of  our  present  knowledge,  such  practice  should  be 
avoided,  not  only  for  the  comfort  of  the  patient,  but  also 
for  the  credit  of  the  practitioner.  In  the  present  state  of 
our  knowledge,  there  is  not  a  single  reason  for  not  correct- 
ing fully  all  the  astigmatism  that  may  be  found  in  any  case ; 
but  not  so  with  the  hypermetropia  and  myopia  that  may 
complicate  it.  The  relationship  between  the  external  and 
internal  recti  should  always  be  known  before  prescribing 
convex  or  concave  spherical  lenses.  This  should  be  deter- 
mined when  the  eyes  are  uninfluenced  by  a  mydriatic* 
The  superior  and  inferior  recti  and  the  obliques  may  not  be 
consulted  when  glasses  are  to  be  prescribed. 

In  prescribing  spherical  lenses  for 

Esophoric  Cases 

there  is  an  absolute  need  for  the  mydriatic  in  its  full  power, 
regardless  of  whether  the  refraction  is  hypermetropic  or 
myopic.     If  hypermetropia  is  associated  with  esophoria,  the 

*See  Ophthalmic  Record,  Vol.  II.,  No.  II. 


NECESSITY   FOR   SUSPENSION   OF   ACCOMMODATION.        239 

accommodation  should  be  fully  suspended,  not  only  that  the 
whole  of  the  refractive  error  may  be  known,  but  that  it  also 
may  be  corrected  fully.  Such  glasses  will  cure  a  part  (the 
pseudo-esophoria)  of  the  esophoric  condition,  if  not  all. 
As  I  have  been  able  to  show  in  a  former  study,  the  esopho- 
ria  associated  with  uncorrected  hypermetropia  is  not  all  due 
to  the  intrinsic  power  of  the  internal  recti.  Further  obser- 
vation leads  me  to  suggest  that,  for  every  dioptre  of  hyper- 
metropia in  each  eye,  there  is  a  half  degree  of  pseudo- 
esophoria  (1  D.  of  H.  in  each  eye  would  give  one  degree). 
What  esophoria  is  left  after  giving  a  full  correction  of  the 
hypermetropia  must  be  cured  by  operation  or  exercise,  or 
by  both.  A  full  correction  of  the  hypermetropia  should  al- 
wa}*s  be  given  in  cases  of  internal  squint. 

When  esophoria  is  associated  with  myopia,  the  mydriatic 
should  be  used  to  full  suspension  of  accommodation,  that 
the  very  great  error  of  giving  an  over-correction  of  the  my- 
opia may  be  avoided.  The  exact  correction  should  be 
known  and  recorded.  The  same  may  be  prescribed  for 
distant  seeing  without  risk  of  adding  a  pseudo-esophoria  to 
the  true  muscle  error;  but  the  fully  correcting  concave 
lenses  should  not  be  prescribed  for  near  use,  for  the  reason 
that  the  muscle  error  would  be  thereby  increased. 

When  the  esophoria  has  been  cured,  the  full  myopic  cor- 
rection should  be  worn  for  all  distances.  In  prescribing 
spherical  lenses  for 


24o     necessity  for  suspension  of  accommodation. 

Exophoric  Cases 
there  is  an  absolute  need  for  the  mydriatic  in  its  full  power,, 
whether  the  refraction  is  hypermetropic  or  myopic ;  for  it  is 
in  these  cases  that  the  true  error  of  refraction  is  most  likely 
to  be  concealed,  because  of  the  spasm  of  accommodation 
caused  by  the  exophoria.  Exophoria  often  causes  em- 
metropic eyes  to  appear  to  be  myopic.  It  renders  latent  the 
greater  part  of  a  hypermetropic  error,  and  adds  a  pseudo- 
myopia  to  the  real  myopia.  The  mydriatic  alone  is  able  to 
show  the  refraction  of  exophoric  eyes  in  its  true  state. 
Without  it  concave  lenses  will  be  selected  by  emmetropic 
eyes;  not  infrequently,  under  these  conditions,  hyperme- 
tropes  choose  concave  lenses.  While  an  over-correction  of 
myopia  should  never  be  given,  the  full  correction  of  a  my- 
opia associated  with  exophoria  should  always  be  prescribed, 
and  the  patient  should  be  directed  to  wear  these  lenses  for 
all  purposes  of  vision. 

While  the  hypermetropia  associated  with  exophoria  should 
always  be  known  and  recorded,  the  full  correction  should 
not  be  given — often  no  correction — until  the  muscle  error 
has  been  cured  by  the  means  at  our  command. 

Orthophoria  is  rare;  but  when  it  exists,  a  full  correction 
of  any  and  all  refractive  errors  should  be  given.  That  an 
over-correction  of  myopia  and  an  under-correction  of  hvper- 
metropia  may  be  avoided  in  these  cases,  the  full  suspension 
of  accommodation  is  essential. 


NECESSITY    FOR    SUSPENSION   OF   ACCOMMODATION.        24I 

Instead  of  using  the  mydriatic  once  in  forty-six  cases,  have 
we  not  strong  scientific  reasons  for  using  it  forty-six  times 
in  forty-six  cases? 

The  human  eye  remains  a  human  eye  under  the  influence 
of  the  mydriatic,  except  as  to  its  focal  adjustment;  in  this 
respect  it  is  no  more  than  a  machine,  and  is  susceptible  of 
perfect  measurement  by  means  of  our  several  objective  and 
subjective  methods.  In  no  other  way  can  accuracy  be  ob- 
tained. 

The  unscientific  cry  of  honest  but  misguided  oculists 
against  the  use  of  the  mydriatic  is,  to  the  ear  of  the  quack 
spectacle  vender,  a  sweet  sound  which  he  attunes  to  his  own 
profit  and  to  the  detriment  of  the  unsuspecting  public.  May 
it  soon  be  heard  no  more  in  the  land ! 
16 


PART  III. 

Operations. 


MUSCLE  SHORTENING  VS.  MUSCLE  ADVANCE- 

MENT.* 

In  doing  advancement  operations  on  the  recti  muscles,  one 
of  the  chief  dangers  to  be  considered  is  turning  the  eyeball 
on  its  antero-posterior  diameter,  in  such  a  way  as  to  throw 
unbearable  strain  on  either  the  superior  or  inferior  oblique 
muscles.  In  addition  to  the  danger  of  "  twisting"  the  eye- 
ball, there  is  the  additional  danger  that  the  knots  may  slip, 
or  the  threads  may  cut  the  conjunctiva  and  sub-conjunctiva 
before  strong  adhesions  have  taken  place  between  tendon  and 
sclera;  and  thus  the  divided  tendon  may  be  pulled  back  even 
beyond  the  point  of  its  original  attachment,  when  the  pa- 
tient's condition  will  be  worse  than  before  the  operation.  In 
DeWecker's  advancement  operation  the  middle  fibres  of  the 
tendon,  which  are  not  divided,  will  prevent  the  tendon's  go- 
ing back  very  far  in  case  the  knots  slip  or  the  threads  cut. 

*  Published  in  the  Ophthalmic  Record,  March,  1S93. 

(243) 


244       MUSCLE    SHORTENING   VS.    MUSCLE   ADVANCEMENT. 

Of  all  advancement  operations,  DeWecker's  is  least  objec- 
tionable, for  the  reason  that  the  two  things  to  be  dreaded  are 
less  likely  to  occur. 

Believing  DeWecker's  operation  to  be  the  best  of  its  class, 
and  thinking  that  some  readers  may  not  have  seen  it  de- 
scribed, I  venture  here  to  give  my  understanding  of  the 
technique  of  this  operation.  The  conjunctiva  is  incised  ver- 
tically over  the  insertion  of  the  tendon,  sufficiently  to  expose 
it  well.  Now  the  upper  and  lower  two-fifths  of  the  tendon 
are  divided  at  their  insertion,  while  the  middle  one-fifth  is 
left  uncut.  With  one  needle  and  one  thread  the  upper  di- 
vided part  of  the  tendon  is  advanced,  the  needle  being  made 
to  penetrate  first  the  tendon,  then  the  conjunctiva  and  sub- 
junctiva  above  and  toward  the  cornea.  A  similar  stitch  is 
then  taken  through  the  divided  lower  part  of  the  tendon  and 
the  conjunctiva  and  sub-conjunctiva  below.  In  tying  these 
stitches  sufficient  force  is  exerted  for  advancing  the  cut  parts 
of  the  tendon  as  far  as  the  judgment  of  the  operator  may 
decide.  The  stitches  are  allowed  to  remain  in  four  to  six 
days,  depending  on  the  amount  of  reaction.  The  undivided 
part  of  the  tendon  serves  a  double  purpose:  i.  It  prevents, 
to  a  great  extent,  the  setting  of  the  tendon  too  high  or  too 
low,  and  in  that  much  avoids  "  twisting"  the  eyeball  on  its 
antero-posterior  axis.  2.  Should  the  knots  slip  or  the  threads 
cut  their  way  out  too  soon,  these  undivided  fibers  prevent 
the   tendon  from   going  very  far  back  behind  the   original 


MUSCLE   SHORTENING  VS.    MUSCLE  ADVANCEMENT.        245 

point  of  attachment.  This  partial  advancement  reminds  one 
of  Stevens's  partial  tenotomies,  the  one  being  the  reverse  of 
the  other. 

DeWecker's  advancement,  the  best  of  all  operations  of  this 
class,  has  been  described,  so  that  a  fair  contrast  may  be 
drawn  between  it  and  my  own  shortening  operation. 

My  operation  for  shortening  a  rectus  muscle  is  simple, 
effective,  and  free  from  the  two  prominent  risks  incurred  in 
any  of  the  advancement  operations.  In  this,  as  in  many 
other  operations  on  the  eye,  cocaine  anesthesia  can  be  relied 
on.  The  first  step  of  the  operation  consists  of  a  vertical 
conjunctival  incision  one-eighth  of  an  inch  behind  the  inser- 
tion of  the  tendon  and  a  little  longer  than  the  muscle  is  wide. 
From  the  lower  extremity  of  this  cut  a  horizontal  conjunc- 
tival incision  is  made  one-fourth  of  an  inch  long,  near  to, 
and  parallel  with,  the  lower  border  of  the  muscle.  The  tri- 
angular flap  of  conjunctiva  is  now  dissected  up,  and  is  held 
out  of  the  way  by  an  assistant.  The  second  step  of  the  op- 
eration consists  in  making  a  puncture  through  the  capsule  at 
the  lower  border  of  the  tendon  and  passing  a  strabismus 
hook  beneath  it  and  then  making  a  slight  puncture  of  the 
capsule  at  upper  border  for  the  exit  cf  the  point  of  the  hook. 
Everything  is  now  ready  for  the  last  operative  procedure,  the 
taking  of  the  stitch  for  shortening  the  muscle.  A  thread  is 
armed  with  two  needles  slightly  curved.  One  needle  is 
passed    through   the    muscle   from  its  outer  surface  and  is 


246       MUSCLE   SHORTENING   VS.    MUSCLE   ADVANCEMENT. 

brought  out  beneath  the  lower  border  of  the  muscle;  the 
other  is  passed  in  the  same  way,  but  is  brought  out  beneath 
the  upper  border  of  the  muscle.  The  capsule  is  included  in 
this  stitch.  The  amount  of  tissue  thus  included  in  the  loop 
need  not  be  more  than  one-fourth  the  width  of  the  muscle ; 
and  the  distance  of  this  loop  behind  the  insertion  of  the 
tendon  must  depend  on  the  amount  of  shortening  desired. 
The  muscle  is  held  away  from  the  globe  by  fixation  forceps 
while  the  needles  are  being  passed  as  above  indicated.  The 
operator  now  taking  the  hook  into  his  own  hand  draws  it 
slightly  back,  and  at  the  same  time  gently  lifts  the  tendon 
from  the  globe.  He  now  takes  needle  No.  1,  and  pierces 
the  tendon  from  the  ocular  side,  at  its  point  of  insertion  and 
between  the  center  and  its  lower  border,  bringing  it  out 
through  the  conjunctiva  over  the  insertion,  then  removes  the 
needle.  In  a  similar  way  needle  No.  2  is  passed  through 
the  tendon  between  its  center  and  upper  border  and  is 
brought  out  through  the  conjunctiva  over  the  insertion. 
This  needle  is  then  removed.  The  two  ends  of  the  one 
thread  need  not  be  more  than  one-eighth  of  an  inch  apart  as 
they  emerge  from  the  tendon.  On  tying  the  knot  in  the 
usual  way,  that  part  of  the  muscle  at  the  loop  is  brought  in 
contact  with  the  tendon  at  its  insertion  and  is  there  confined 
by  completing  the  knot.  The  triangular  flap  of  conjunctiva 
is  now  allowed  to  fall  and  cover  in  the  exposed  muscle,  in- 
cluding its  "  tuck."     The  stitch  is  allowed  to  remain  from 


MUSCLE  SHORTENING  VS.   MUSCLE  ADVANCEMENT.        247 

four  to  six  days,  depending  on  the  inflammatory  action  ex- 
cited. The  stitch  will  excite  sufficient  inflammation  to  bind 
the  parts  in  their  new  relationship ;  and  thus  the  shortening 
is  made  permanent.  As  in  advancements  so  in  the  shorten- 
ing, it  is  often  necessary  to  do  either  a  partial  or  a  complete 
tenotomy  of  the  opposing  muscle. 

A  muscle  thus  shortened  is  not  likely  to  "  twist  "  the  eye- 
ball; if  the  twisting  occur,  it  would  be  but  slight  as  compared 
with  the  result  of  an  ordinary  advancement.  The  stitch  ta- 
ken in  the  tendon  will  not  cut  its  way  out,  as  is  so  common 
when  taken  in  the  conjunctiva  and  sub-conjunctiva,  there- 
fore there  will  be  no  slipping  back  of  the  muscle  from  this 
cause.  Should  the  knot  untie,  the  muscle  cannot  go  farther 
back  than  before ;  for  no  part  of  it  has  been  cut  loose  from 
its  original  attachment.  The  "knuckle  of  muscle"  made 
by  the  operation  undergoes  absorption,  so  that  in  a  few 
weeks  the  parts  become  smooth  at  the  site  of  the  operation. 

The  operation  described  above  I  have  done  many  times, 
with  much  satisfaction.  Even  if  it  had  been  devised  by 
some  one  else,  I  think  I  would  still  prefer  it  over  the  very 
best  advancement  operations,  and  for  the  reasons  given. 


248  MUSCLE   SHORTENING. 

INDICATIONS    FOR,    AND    ADVANTAGES    AND 
TECHNIQUE  OF,  MUSCLE  SHORTENING. 

In  the  judgment  of  the  author  of  this  paper,  muscle  short- 
ening is  indicated  in  all  cases  of  heterotropia,  regardless  of 
the  direction  or  extent  of  the  turning.  In  many  cases  of 
low  degrees  of  squint,  the  shortening  operation  alone  will  ef- 
fect a  cure  ;  while,  in  a  greater  number  of  cases,  the  shorten- 
ing of  the  weaker  muscle  should  be  associated  with  a  partial 
division  of  the  tendon  of  the  stronger  muscle,  in  order  to  the 
attainment  of  the  best  results.  In  cases  of  high  degree  of 
exophoria,  in  which  a  partial  tenotomy  of  both  external 
recti  does  not  reduce  the  exophoria  within  the  range  of 
possibility  of  completing  the  cure  by  rhythmic  exercise  of  the 
interni,  the  latter  should  be  shortened.  In  all  cases  of  ex- 
ophoria, with  less  than  8°  of  abduction,  shortening  of  the 
interni  is  indicated,  not  to  be  associated  with  even  the  slight- 
est tenotomy  of  the  externi.  In  high  degrees  of  esophoria, 
not  reduced  by  a  partial  tenotomy  of  the  interni  within  the 
limit  of  possibility  of  completing  the  work  by  exercising  the 
externi,  the  latter  should  be  shortened;  while  in  the  lower 
degrees  of  esophoria,  the  only  operation  indicated  is  the 
shortening  of  the  externi.  In  any  case  of  hyperphoria,  not 
reduced  to  2°  or  less  by  a  partial  tenotomy  of  the  superior 
rectus  of  the  hyperphoric  eye,  the  inferior  rectus  of  that  eye 
should  be  shortened.  In  all  cases  where  shortening  is  indi- 
cated, except  in  hypertropia  and  hyperphoria,  the  operative 


MUSCLE   SHORTENING.  249 

effect  should  be  divided  between  the  corresponding  muscles 
of  the  two  eyes.  The  superior  and  inferior  recti  of  a  cata- 
phoric eye  should  be  operated  on  rarely  if  ever.  Since  the 
shortening  of  the  recti  muscles,  associated  with  partial  tenot- 
omies of  the  opposing  muscles  can  effect  so  much,  a  com- 
plete tenotomy  of  an  ocular  muscle  cannot  be  often  indicated. 

The  Advantages  of  Shortening 
a  muscle  over  the  older  method  of  muscle  advancement  may 
be  set  forth  in  a  few  words.  The  former  is  the  more  easily 
done,  and  is  the  safer  of  the  two  operations,  in  that  torsion 
of  the  eye  is  not  so  likely  to  occur  as  a  result  of  setting  the 
tendon  too  high  or  too  low,  in  case  the  externi  or  the  interni 
are  the  muscles  involved;  or  too  far  out  or  in,  when  the  su- 
perior and  inferior  recti  are  the  muscles  in  question.  Should 
the  knot  come  untied  in  the  shortening  operation,  the  patient's 
condition  will  not  be  worse  after  the  operation  than  before, 
which  cannot  always  be  said  when  the  same  thing  happens 
in  the  attempt  to  advance  a  muscle.  An  apparent  objection 
to  the  shortening  operation  is  the  knuckle  of  the  muscle 
formed  by  the  folding.      This  disappears  by  absorption. 

The  Technique  of  Muscle  Shortening 
was  simple  when  first  introduced,  but  has  grown  in  simplici- 
ty as  a  result  of  a  modification  suggested  and  practiced  by 
Dr.  Tenney,  of  Boston.  The  original  operation  was  per- 
formed as  follows:  The  eye  was  cocainized;  the  lids  were 
separated  by  a  stop  speculum;   the  conjunctiva  was  seized 


25O  MUSCLE   SHORTENING. 

with  fixation  forceps  a  little  behind  the  insertion  of  the  mus- 
cle tendon,  and  two  cuts  with  scissors  were  made:  one  verti- 
cal the  entire  width  of  the  tendon  and  a  little  behind  the  in- 
sertion, the  other  below  and  parallel  with  the  lower  border 
of  the  tendon  and  muscle.  The  included  portion  of  the 
conjunctiva  was  then  dissected  up  and  held  out  of  the  way. 
A  puncture  of  the  capsule  of  Tenon  was  next  made,  at  the 
lower  border  of  the  tendon  near  its  insertion,  and  another 
puncture  at  a  corresponding  point  at  the  upper  border  of  the 
tendon,  through  which  a  strabismus  hook  was  passed  be- 
neath the  tendon,  with  which  to  control  the  eye.  A  silk 
thread  was  then  armed  with  two  needles,  one  of  which  was 
passed  through  the  upper  part  of  the  muscle  and  capsule 
from  without  in,  at  a  chosen  distance  behind  the  insertion, 
and  similarly  the  other  needle  was  passed  through  the  lower 
part  of  the  muscle  and  capsule  at  a  point  immediately  in  line 
with  the  first.  Drawing  on  the  two  ends,  a  loop  of  thread 
was  brought  in  contact  with  the  capsule  over  the  muscle. 
The  passage  of  these  needles  was  facilitated  by  lifting  the 
respective  borders  of  the  muscle  with  fixation  forceps.  The 
next  step  of  the  operation  was  to  lift  the  tendon  by  means  of 
the  hook,  and  pass  first  one  needle  and  then  the  other 
through  the  tendon  from  within  out  at  points  one-eighth  of 
an  inch  apart,  bringing  these  needles  out  through  the  con- 
junctiva a  little  in  advance  of  the  tendon  insertion.  The 
two  needles  were  now  removed,  and  by  means  of  the  sur- 
geon's knot  the  part  of    the  muscle  beneath   the   loop  of 


MUSCLE   SHORTENING.  25 1 

thread  was  drawn  up  to  the  insertion  of  the  tendon,  thus 
shortening  the  muscle  to  a  corresponding  extent.  The  flap 
of  conjunctiva  was  now  allowed  to  fall  down  over  the 
knuckle  of  muscle.  The  stitch  was  allowed  to  remain  from 
four  to  six  days,  at  the  end  of  which  time  the  muscle  was 
fixed,  by  adhesive  inflammation,  in  its  new  relation. 

The  modification  suggested  by  Dr.  Tenney  in  a  personal 
letter  I  at  once  adopted.  As  thus  modified  the  operation  is 
done  as  follows:  A  horizontal  cut  is  made  with  scissors 
through  the  conjunctiva  and  capsule  of  Tenon,  beneath  the 
lower  border  of  the  muscle,  from  the  insertion  of  the  tendon 
backward,  to  the  extent  of  the  shortening  desired.  Through 
this  cut,  two  strabismus  hooks  are  passed:  one  beneath  the 
tendon  at  its  insertion,  the  other  beneath  the  muscle.  By 
means  of  these  hooks  the  muscle  is  lifted  from  the  sclera. 
A  needle  is  now  passed  through  the  conjunctiva  and  the  up- 
per border  of  the  tendon  at  its  insertion,  and  is  carried  back 
beneath  the  muscle  to  a  point  chosen  just  in  advance  of  the 
second  hook,  where  it  is  made  to  penetrate  the  muscle  near 
its  upper  border  and  the  superposed  capsule  and  conjunctiva. 
The  needle  was  then  made  to  reenter  the  puncture  in  the 
conjunctiva  made  by  it  in  its  exit,  is  directed  downward  be- 
tween the  conjunctiva  and  the  capsule,  and  is  brought  out 
through  the  incision  in  the  conjunctiva.  Then  the  lower  bor- 
der of  the  muscle  and  capsule  are  seized  with  forceps,  and 
this  needle  is  made  to  penetrate  them  from  without  in,  and 
is  again  brought  out  through  the  horizontal  incision.     The 


252  A   NEW   OPERATION   FOR   PTERYGIUM. 

needle  is  now  passed  through  the  incision  beneath  the  ten- 
don, which  it  is  made  to  penetrate  at  the  lower  border  of  its 
insertion,  and  is  brought  out  through  the  conjunctiva  at  a 
point  in  line  with,  and  one-eighth  of  an  inch  below,  the 
primary  puncture.  The  two  ends  of  the  suture  thus  passed 
are  now  brought  together  by  a  surgeon's  knot  with  enough 
force  to  bring  the  part  of  the  muscle  beneath  the  loop  in 
contact  with  the  tendon.  The  suture  is  allowed  to  remain 
from  four  to  six  days. 

The  suture  plate,  as  modified  and  improved  by  Dr.  George 
H.  Price,  will  most  likely  be  of  much  service  in  this  opera- 
tion, if  for  no  other  reason  than  that  it  will  greatly  facilitate 
the  removal  of  the  suture.  The  improved  plate  is  made  of 
aluminum,  is  five-sixteenths  of  an  inch  long,  and  one-eighth 
of  an  inch  wide,  oval  in  shape.  In  this  plate  there  are  two 
holes  one-eighth  of  an  inch  apart,  through  which  the  two 
ends  of  the  suture  are  passed.  In  trying  the  suture,  the 
plate,  which  has  such  a  concavity  as  to  fit  the  curvature 
of  the  eye,  is  brought  in  contact  with  the  eye,  and  the  knot 
is  tied  over  it  between  the  two  holes.  There  is  a  transverse 
groove  near  one  hole,  along  which  one  blade  of  the  scissors 
in  passed  when  the  suture  is  to  be  removed. 


A  NEW  OPERATION  FOR  PTERYGIUM  * 
Perhaps  every  operator  who  has  had  much  experience  in 

*  Published  in  the  Ophthalmic  Record,  March,  1S93. 


A    NEW    OPERATION    FOR    PTERYGIUM. 


253 


removing  this  growth  has  now  and  then  seen  it  return  in 
spite  of  the  care  exercised  in  the  operation.  It  is  generally 
conceded  that  the  return  of  the  growth  is  due  to  some  part  of 
the  ocular  conjunctiva  attaching  itself  to  the  denuded  sur- 
face of  the  cornea;  and,  with  this  thought  in  mind,  opera- 
tors are  usually  careful  not  to  cause  the  conjunctiva  to  overlap 
the  cornea,  when  they  bring  the  margins  of  the  conjunctival 
wound  together  with  stitches.  The  object  of  this  publica- 
tion   is    to   call   attention   to   a  little    device  of   my  own,   as 

effective  in  preventing  a  return 
of  the  growth  as  it  is  simple  in 
execution.  The  growth  can  be 
removed  in  any  one  of  the  sev- 
eral ways  recommended  by  dif- 
ferent operators.  This  done, 
my  device  consists  in  making  a  vertical  incision  above  and 
below,  each  about  one-eighth  of  an  inch  long  and  about 
one-tenth  of  an  inch  from  the  most  projecting  part  of 
the  denuded  margin  of  the  cornea.  Before  the  vertical  cuts 
are  made,  the  two  conjunctival  stitches  should  be  taken  in 
the  usual  way  for  covering  the  exposed  sclera.  When  these 
are  tied,  the  parts  are  brought  together  without  throwing  the 
conjunctiva  near  the  corneal  margin  into  folds.  As  can  be 
seen,  there  is  the  minimum  of  danger  that  any  of  the  con- 
junctiva will  become  attached  to  the  cornea  before  it  is  cov- 
ered by  epithelium. 


254  A    NEW    OPERATION    FOR    PTERYGIUM. 

For  the  best  results  in  the  way  of  leaving  a  clear  cornea, 
the  corneal  part  of  the  pterygium  should  always  be  removed 
by  traction,  never  by  dissection.  My  method  of  removing 
the  growth  is  to  seize  the  pterygium  with  fixation  forceps  at 
the  corneo-scleral  junction;  lifting  it  gently,  I  make  punc- 
tures with  a  Grafe  knife  through  healthy  conjunctiva  imme- 
diately above  and  below  the  growth  at  the  corneal  margin. 
Through  the  puncture  below,  while  still  holding  the  growth, 
with  the  forceps,  I  pass  one  blade  of  a  straight  pair  of  scis- 
sors toward  the  canthus  sufficiently  far  to  include  all  that  I 
wish  to  remove,  and  bringing  the  two  blades  together  I  make 
the  first  incision  obliquely  up.  In  a  similar  way  I  enter  the 
puncture  above,  and  cutting  obliquely  down  and  toward  the 
canthus,  complete  a  V-shaped  incision.  The  part  of  the 
growth  thus  included  is  carefully  dissected  up  to  the  corneal 
margin,  but  no  farther.  Grasping  this  freed  portion  of  the 
pterygium  firmly  with  the  fixation  forceps,  I  direct  the  pa- 
tient to  look  strongly  in  the  direction  of  the  base  of  the 
growth  while  I  make  forcible  traction  toward  its  apex.  In 
this  way  the  removal  is  easily  effected  without  leaving  any 
shreds  behind.  This  is  infinitely  better  than  the  most  care- 
ful dissection  could  be.  Irregularities  of  the  denuded  sur- 
face are  soon  filled  in  with  plastic  material,  and  the  whole  is 
covered  by  epithelium  in  very  few  days. 


ARTIFICIAL   PUPIL  THROUGH    SOFT   CATARACT.  255 

ARTIFICIAL  PUPIL  THROUGH  THE  CENTER  OF 
SOFT  CATARACT. 

In  1888  I  published  in  the  Nashville  Journal  of  Medicine 
and  Surgery  a  description  of  the  above-named  operation, 
using  as  an  illustration  the  accompanying  cut,  which  was 
made  from  life.  The  patient  on  whom  I  did  the  first  oper- 
ation (the  one  represented  in  the  cut)  was  a  girl  about  six- 
teen years  old,  who  had  been  blind  for  four  or  more  years, 
the  cataract  developing  after  an  attack  of  typhoid  fever. 
After  the  usual  method  described  in  text-books,  I  made  the 
first  opening  in  the  capsule  of  each  eye  with  one  needle; 
after  resulting  irritation  had  passed  away,  I  made  a  second 
operation  with  one  needle,  stirring  up  the  lens  substance 
somewhat,  so  as  to  hasten  its  solution.  By  the  end  of  an- 
other two  weeks  a  considerable  portion  of  each  lens  had  been 
dissolved,  and  no  excitation  had  followed  the  second  opera- 
tion. Now,  with  the  view  of  still  further  hastening  the  solu- 
tion of  the  cataracts,  I  again  introduced  one  needle  to  stir 
the  lens  substance.  While  the  needle  was  in  the  first  eye 
the  thought  occurred  to  me  that  it  would  be  safe  to  introduce 
a  second  needle  and,  bringing  the  two  together  in  the  center 
of  the  partly  dissolved  cataract,  make  an  opening  through  it 
by  a  process  of  tearing  and  packing  the  substance  toward 
the  ciliarv  processes,  without  danger  of  pressing  against 
them.     I  called  for  a   second  needle  and  at    once  put  the 


256 


ARTIFICIAL    PUPIL   THROUGH    SOFT   CATARACT. 


thought  into  execution  in  that  and  the  fellow-eye,  and  with 
the  results  shown  in  this  cut. 

The  patient  was  able  to  see  at  once ;  and  hardly  any  irri- 
tation followed  the  operation.  I  watched  anxiously,  fearing 
that  the  lens  material  might  become  loose  and  fill  the  open- 
ing I  had  made.  On  the  contrary,  by  the  solvent  action  of 
the    aqueous    the    opening   was   made   larger   day  by  day. 


Within  a  week  after  making  the  pupils  I  had  fitted  my  pa- 
tient with  lenses,  giving  her  vision  =  ~°,  and  sent  her  home. 
She  went  about  seeing  while  the  remaining  parts  of  the  cat- 
aracts were  undergoing  solution,  which  took  several  weeks 


longer. 


I  have  since  done  the  operation  often,  and  always  with 
success.     Similar  reports  have  come  to  me  from  others. 

The  opening  should  not  be  made,  in  the  manner  described, 
earlier  than  the  third  needling,  which,  as  a  rule,  is  from  four 


OPERATION   FOR   ENTROPION   AND   TRICHIASIS.  257 

to  six  weeks  after  the  first  operation;  and  not  then  unless 
about  half  the  material  has  been  dissolved.  The  danger  in 
attempting  it  too  early  would  be  that  the  packing  process 
might-  cause  undue — even  injurious — pressure  on  the  ciliary 
body. 


THE   SIMPLEST  AND  BEST  OPERATION  FOR  THE 
CURE  OF  ENTROPION  AND  TRICHIASIS. 

At  the  time  I  described  my  double-stitch  method  of  oper- 
ating for  the  cure  of  entropion,*  I  was  not  aware  that  Dr. 
John  Green  had  preceded  me  in  the  device  of  this  most  ef- 
fective means  of  everting  the  ciliary  margin,  after  either  a 
simple  Burow  incision  or  a  Flarer's  inter-marginal  incision. 

My  method  of  operating  at  that  time  is  shown  in  the  ac- 
companying cut  A,  which  I  reproduce. 

As  may  be  seen,  I  made  the  inter-marginal  incision,  and 
then  took  several  double  stitches  as  shown,  tying  first  the 
middle  suture  and  then  those  on  either  side.  The  stitches 
were  not  removed  until  the  wedge-shaped  incision  had  be- 
come filled   with  plastic  material.     The   chief  difficulty   in 

*In  Nashville  Journal  of  Medicine  and  Surgery ,  early  in  1888. 
17 


258 


OPERATION  FOR   ENTROPION  AND   TRICHIASIS. 


this  operation  was  in  making  the  inter-marginal  incision,  be- 
cause of  the  narrowed  and  otherwise  deformed  lid  margin. 
For  this  reason  I  soon  abandoned  Flarer's  incision,  and  as- 
sociated the  double  stitch  with  Burow's  incision,  as  Green 
had  before  done,  but  not  to  my  knowledge.  My  stitch  al- 
ways differed  from  Green's,  in  that  I  made  the  needle  enter 


Figure  A. 


the  Burow  incision,  as  I  had  before  made  it  enter  the 
Flarer  incision,  and  thus  included  structure  that  the 
thread  was  not  likely  to  cut  through.  Green's  first  stitch 
was  taken  to  only  a  slight  depth  through  the  outer  lip  of  the 
lid  margin,  and  therefore  readily  cut  its  way  out,  often  too 
soon.  Our  second  stitches  are  identical.  I  continued  to  do 
this  operation  until  a  year  ago,  when  the  thought  of  a  most 
important    modification    occurred    to    me,   a   description  of 


OPERATION   FOR   ENTROPION   AND   TRICHIASIS. 


259 


which  was  published  in  No.  7,  Vol.  II.,  of  the  Ophthalmic 
Record.  Cut  B  shows  the  modification,  and  the  reasons 
for  it  will  be  apparent. 

Having  made  the  Burow  incision 
in  the  usual  way,  I  then  made  four 
vertical  cuts  through  the  freed 
margin  of  the  lid  through  all  the 
structures  to  the  skin.  While  the 
Figure  B.  Burow    incision    widens    the    de- 

formed tarsus,  the  vertical  cuts  lengthen  the  freed  marginal 
part  of  the  tarsus  (I  am  not  sure  but  that  the  vertical  cuts 
should  extend  entirely  across  the  tarsus),  which  is  a  great 
gain.  A  great  advantage  gained  by  the  vertical  cuts  is  that 
they  greatly  facilitate  the  out-turning  of  the  eyelashes,  so 
that  the  Burow  incision  may  become  filled  with  a  large  mass 
of  plastic  material.  Another  decided  advantage  is  that,  in 
most  cases,  the  double  stitch — all  stitches — may  be  dis- 
pensed with.  The  accompanying 
cut  C,  shows  how  effectively  the 
lid  margin  may  be  held  in  the 
everted  position  by  means  of  a 
narrow  strip  of  surgeons'  rubber 
adhesive  plaster.     The  use  of  the 


Figure  C. 

plaster  was  suggested  to  me  by  my  office  associate,  Dr. 
George  H.  Price.  I  have  constantly  employed  the  plaster  in 
connection  with  the  longitudinal  and  vertical  cuts  for  about 


260 


OPERATION   FOR   ENTROPION   AND   TRICHIASIS. 


one  year.  There  are  few  operations  that  are  more  uniform- 
ly successful.  With  the  T-shaped  forceps  and  a  sharp 
knife,  the  operation  is  quickly  and  easily  performed.  When 
the  eyelashes  are  short  and  few,  the  double  stitch  must  be 
substituted  for  the  plaster. 

Finding  the  T  forceps  not  all  that  could  be  desired,  I 
devised  the  stirrup  forceps  shown  in  the  accompanying  cut. 
In  every  way  the  latter  is  superior  to  the  former.     The  lid, 


^B 


when  properly  grasped  with  the  stirrup  forceps,  is  easily 
manipulated.  The  shoulders  extending  from  the  foot  piece 
a  short  distance  up  each  arm  of  the  stirrup,  serve  to  compress 
the  margin  of  the  lid  so  as  to  render  the  operation  a  blood- 
less one.  Free  bleeding  occurs  after  the  removal  of  the 
forceps.  The  Burow  incision  should  be  made  obliquely 
from  within  out  and  toward  the  free  margin  of  the  lid,  and 
only  far  enough  within  the  lid  to  avoid  wounding  the  hair 
follicles.  The  incision  should  include  the  entire  length  of 
the  cartilage.  One  vertical  cut  at  each  end  of  the  Burow 
incision  is  usually  enough. 


TO   NARROW   THE   PALPEBRAL   FISSURE.  26l 

TO  NARROW  THE  PALPEBRAL  FISSURE. 

The  operation  for  narrowing  and  shortening  the  palpe- 
bral fissure  is  not  often  necessary,  but  when  we  have  it  to 
do  we  want  it  to  be  successful.  Paring  the  margins  of  the 
upper  and  lower  lids  at  the  outer  canthus  by  means  of  scis- 
sors or  knife  is  not  always  easily  and  thoroughly  done. 
Some  epithelial  cells  are  left  that  prevent  strong  and  exten- 
sive adhesions,  after  the  most  careful  stitching.  Partial  or 
complete  failures  are  frequent  as  compared  with  the  number 
of  these  operations. 

I  had  a  patient  recently  whose  facial  nerve  had  been 
wounded  when  a  child,  after  which  he  had  not  been  able 
to  close  the  eye  of  that  side.  During  waking  hours  that 
eye  was  always  more  widely  open  than  the  fellow-eye.  To 
relieve  him  of  this  deformity  and  to  give  better  protection  to 
the  cornea,  I  advised  an  operation.  The  attempt  after  the 
usual  method  was  a  failure.  He  wras  willing  to  try  again, 
but  wanted  no  failure  this  time.  It  occurred  to  me  to  use 
the  galvano-cautery  in  order  to  get  the  two  raw  surfaces. 
After  cocainizing  the  eye,  I  protected  the  globe  with  the 
horn  spatula  and  applied  a  cautery  point  of  proper  length 
and  width,  and  made  a  free  burn  on  lid  margin  behind  the 
lashes.  I  made  a  similar  burn  on  the  fellow-lid.  I  then  re- 
moved the  charred  tissue  by  scraping  with  a  knife,  and 
stitched  the  two  raw  surfaces  together.  Perfect  adhesion 
formed,  and  the  result  was  good. 


metfa 

°f   Optometrists 

INDEX. 

Accommodation,  Page 

how  it  may  be  increased  by  rhythmic  exercise 181 

spasm  of 136 

the  guiding  sensation  master  of 125 

the  power  of,  restrained  by  the  guiding  sensation 126 

the  necessity  for  suspension  of,  in  refraction  work 223 

reasons  against  suspension  of,  not  well  founded  in  the  main 223 

Accommodation  and  Convergence, 

relationship  between  centers  of 124 

dissociation  of 127 

the  relationship  between,  may  be  disturbed  by  hypermetropia  ....  128 

by  esophoria 129 

by  a  mydriatic 131 

by  intrinsic  exophoria 135 

Astigmatism, 

denned  and  illustrated 2 

regular,  its  origin  and  duration 6 

the  effect  of,  on  retinal  images 6 

vertical  and  horizontal,  blurs  but  does  not  distort  images  of  vertical 

and  horizontal  objects 7 

non-oblique,  what  the  correcting  cylinder  does  to  the  image iS 

non-oblique,  the  character  of  work  done  by  eyes  for  sharpening 

retinal  images  in 13 

non-oblique,    symptoms    dependent   on,    pass   away  in    advancing 

years 17 

oblique,  the  character  of  work  done  for  harmonizing  images  in  .  .  .  14 

oblique,  what  the  correcting  cylinder  does  to  the  image iS 

why  the  non-oblique  is  less  annoying  than  the  oblique 16 

oblique,  the   conditions  determining  the  quantity  of  distortion  of 

retinal  images  in iS 

oblique,  metamorphopsia    in,  through    correcting    cylinders,    how 

caused,  and  how  cured 21,  61 

oblique,  Steele's  rule  for  placing  the  axes  of  the  cylinders --,  57 

(263) 


264  INDEX. 

Astigmatism  (Continued),  Page 

oblique,  meridians  of  greatest  curvature  diverging,  the  action  of  the 

superior  oblique  in,  illustrated 36 

oblique,  meridians  of  greatest  curvature  converging,  the  action  of 

the  inferior  obliques  in 37 

oblique,  artificial  and  natural,  cause  like  image  changes 38 

oblique,  of  any  kind,  meridians  of  greatest  curvature  diverging,  call 

into  action  the  superior  obliques 39 

oblique,  blurs  and  distorts  images  of  vertical  and  horizontal  lines. .        8 

oblique,  the  rule  for  the  distortion  of  images  in 12 

oblique,  the  distortion  of  images  in,  demonstrable 12 

oblique,  of  anv  kind,  meridians  of  greatest  curvature  converging, 

call  into  action  the  inferior  obliques 39 

oblique,  meridians  of   greatest  curvature  vertical  and    horizontal, 

least  troublesome 40 

oblique,  meridians  of  greatest  curvature  converging,  more  trouble- 
some      40 

oblique,  meridians  of   greatest    curvature    diverging   above,  most 

troublesome 40 

oblique,  why  the  correction  of,  in  some  cases  adds  to  the  patient's 

discomfort 60 

Camera,  The, 

and  the  human  eye 82 

Diplopia, 

nature's  two  methods  of  preventing 3§ 

Direction, 

the  law  of 1S3 

the  law  of,  how  modified 186 

the  center  of,  illustrated 184 

the  line  of,  a  radius  of  retinal  curvature  prolonged 186 

the  law  of,  supreme  in  monocular  vision 1S7 

the  law  of,  how  interfered  with  in  astigmatism,  illustrated 36 

the  law  of,  interfered  with  by  prisms  in  positions  of  rest 189 

Esophoria, 

intrinsic 129>  *35 

pseudo I3° 


INDEX.  265 

Esophoria  (Continued),  Page 

sthenic,  diagnosis  of 172 

treatment  of,  by  hypermetropic  correction , 172 

by  esophoric  prisms 172 

by  partial  tenotomies  of  interni 173 

asthenic,  diagnosis  of 173 

treatment  of 173 

by  esophoric  set  and  by  wall-to-wall  exercise 173 

by  partial  tenotomies  never 173 

by  shortening  the  externi 174 

in  the  far  and  exophoria  in  the  near,  always  asthenic 175 

treatment  of,  by  prism  exercise 175 

by  wall-to-wall  exercise 176 

technique  of  operation  for 220 

treatment  of,  by  rhythmic  exercise 152,  159 

cases  of,  not  suited  to  exercise  treatment 157 

Exophoria, 

treatment  by  rhythmic  exercise :  (1)  by  the  wax  taper  method  ....  149 

(2)  by  the  exophoric  set  of  prisms 151,  159 

cases  of,  not  suited  to  exercise  treatment 156 

sthenic,  diagnosis  of 169 

treatment  of,  by  operation 170 

by  exercise 1 70 

asthenic,  diagnosis  oi 171 

treatment  of,  by  exercise  prisms 171 

by  wall-to-wall  exercise 172 

by  Price's  prisms 172 

Eye-strain, 

denned 225 

of  intrinsic  and  extrinsic  muscles 225 

ciliary 229 

in  prescribing  glasses  for,  both  the  focal  and  muscle  error  must  be 

considered 226 

character  of,  in  hypermetropia 227 

in  myopia 227 

in  non-oblique  astigmatism 227 

in  oblique  astigmatism 22S 


266  INDEX. 

Heterophoria,  Page 

lateral,  when  not  to  test 132 

sthenic  and  asthenic 164 

different  theories  for 197 

tests  for  determining 200 

time  to  test  for  lateral 132,  200 

the  red  glass  test  of 209 

latent,  does  it  exist? 214 

how  to  deal  with  it 215 

the  development  of,  limited 216 

the  safe  line  between  operative  and  non-operative  cases  of 212 

the  safe  line  not  always  a  sufficient  line 214 

the  technique  of  operating  for  cure  of 217 

a  complete  tenotomy  should  not  be  done  for 216 

a  second  operation  on  the  same  muscle  wrong  in 216 

interval  between  operations 217 

Hypermetropes, 

why  some  wear  concave  glasses  more  comfortably  than  convex. . .  137 

Hypermetropia, 

rules  for  correcting:  (1)  when  there  is  esophoria 130 

(2)  when  there  is  exophoria 136 

(3)  when  there  is  squint 133 

Norton's  rules  for  correcting .      141 

and  myopia,  safe  and  easy  rules  for  correcting 13S 

Hyperphoria, 

treatment  of,  by  hyperphoric  set  of  prisms 153,  159 

cases  of,  not  suited  to  exercise  treatment 15S 

technique  of  operation  for 218 

sthenic,  diagnosis  of 1 74 

treatment  of,  by  operation 174 

by  hyperphoric  prisms 1 74 

asthenic,  diagnosis  of 175 

treatment  of,  by  partial  tenotomy  never 175 

by  hyperphoric  prisms 175 

by  ceiling-to-floor  exercise 175 

Image  of  a  Rectangle, 

in  a  non-astigmatic  eye,  as  shown  by  photography 84 


INDEX.  267 

Image  of  a  Rectangle  (Continued),  Page 

in  an  oblique  astigmatic  eye,  meridian  of  greatest  curvature  at  450, 

illustrated 84 

in  an  astigmatic  eye,  meridian  of  greatest  curvature  vertical,  illus- 
trated       85 

in  an  oblique  astigmatic  eye,  meridian  of  greatest  curvature  at  1350, 

illustrated 85 

in  horizontal  astigmatism,  illustrated 87 

Images, 

distortion  of,  by  oblique  astigmatism,  relieved  by  correct  and  prop- 
erly placed  cylinders 4S,  61 

distorted  by  displaced  cylinder  axes 46 

arc  of  distortion  of,  by  plus  cylinders,  for  the  superior  obliques. ...     53 

by  plus  cylinders  for  the  inferior  obliques 53 

by  minus  cylinders . 60 

obliquity  of,  in  oblique  astigmatism  proved 

by  experiment 65 

by  clinical  observation 67 

by  physiologic  optics 68,  75 

by  photography 84,  85,  92,  93,  95 

fusion  of  horizontal  lines  of,  in  oblique  astigmatism,  more  impor- 
tant than  fusion  of  vertical  lines,  proved  by  experiment 70 

by  clinical  observation 71 

Line  of  Direction, 

not  the  axial  ray  prolonged 79 

a  radius  of  retinal  curvature  prolonged So,  184 

Lowry  and  His  Camera 82 

Maddox  Rod,  Proper  Form  of 201 

Maddox  Double  Prism,  Modification  of 203 

Metamorphopsia, 

through  correcting  cylinders  in  vertical  and  horizontal  astigma- 
tism does  not  occur 74 

exists,  but  rapidly  disappears,  when  axes  of  plus  cylinders  must  di- 
verge above 42 

exists,  and   slowly  disappears,   when  axes  of  plus   cylinders   must 

converge  above , 74 

greater  through  an  oblique  cylinder,  held  at  a  distance  from,  than 
when  near  to,  the  eye  explained 7S 


268  INDEX. 

Page 

monoscopter 192 

Muscle,  Ciliary, 

regular  and  sectional  contraction  of 13 

Muscles, 

the  recti,  designed  to  control  the  visual  axes ,  24 

the  oblique,  concerned  only  with  the  corneo-retinal  meridians  ....  24 

the  extrinsic  ocular,  and  the  axes  around  which  they  rotate  the  eye.  25 

common  purpose  of  all,  binocular  single  vision 27 

the  lateral  recti,  and  what  they  do 25,  26 

errors  of  attachment  of 26 

the  vertically  acting  recti,  and  what  they  effect 26 

the  extrinsic  ocular,  their  action  in  non-astigmatic  eyes,  illustrated.  28 

the  recti,  the  strength  test  of 207 

the    oblique,    their   action    in    oblique    astigmatism,    meridians    of 

greatest  curvature  converging,  illustrated 34 

the  simple  function  of 25 

the  complicated  function  of 31 

artificial  means  of  exciting  their  simple  function    42,  103 

artificial  means  of  exciting  their  complicated  function 44 

work  taken  from  the  inferior,  by  the  correction  of  oblique  as- 
tigmatism, transferred  to  the  superior 57 

this  work  transferred  by  degrees  from  the  one  to  the  other 

(1)  by  revolving  the  fully  correcting  cylinders  in  arcs  of 
distortion  for  the  inferior  obliques 58 

(2)  by  giving  only  a  partially  correcting  cylinder  at  first 
and  gradually  increasing  to  the  full  strength,  placing 
axes  over  best  meridians 61 

a  device  showing  the  symmetric  action  of,  and  measuring  the 

extent  of  rotation  by 96 

an  ocular  demonstration  of  their  symmetric  action  because  of 

displaced  images  on  the  retinae 97 

insufficiency  of,  when  discovered 100 

how  to  detect  by  means  of  the  double  prism 101 

how  to  detect  with  the  Wilson  phorometer 121 

how  to  detect  with  a  single  prism,  base  up  or  down 123 

probable  causes  of,  in  some  cases 116,  122 

symmetrical 104 

nonsymmetrical 104 


INDEX.  269 

Muscles  (Continued),  Page 

the  oblique,  insufficiency  of  (continued), 

may  be  caused  by  error  of  attachment  of  interni 122 

both    the    superior  and    inferior    may   be  weak,  and    how 

shown 123 

treatment  of,  when  discovered 107 

how  to  treat .    113,  118,  155 

evidences  in  favor  of  the  treatment  of 120 

how  to  place  astigmatic  lenses  so  as  to  favor  weakness  of  57,  61 
Muscular  Exercise, 

by  Dyer's  method 143 

by  Michel's  method 144 

by  Steven's  method 145 

by  the  rhythmic  method 147 

Mydriatics, 

why  some  patients  suffer  more  pain  from  their  use  than  others. . . .  137 
Operations, 

(1)  muscle  shortening  vs.  muscle  advancement 243 

(2)  indications  for,  advantages  and  technique  of  muscle  shortening.  248 

(3)  pterygium,  a  new  operation  for  ....    252 

(4)  artificial  pupil  through  center  of  soft  cataract 255 

(5)  entropion  and  trichiasis,  simplest  and  best  operation  for 257 

(6)  for  narrowing  the  palpebral  fissure 261 

Orthophoria, 

sthenic,  diagnosis  of 164 

asthenic  lateral,  diagnosis  of 165 

treatment  of,  by  prisms , 165 

treatment  of,  by  wall-to-wall  exercise 166 

sthenic  vertical,  diagnosis  of 165 

asthenic  vertical,  diagnosis  of 167 

treatment  of,  by  prisms 169 

treatment  of,  by  ceiling-to-floor  exercise 168 

Perry  and  His  Camera 91 

Presbyopia, 

causes  of 177 

treatment  to  delay 179 

other  benefits  to  result  from  this  treatment 180 


27O  INDEX. 

Prescribing  Lenses,  Page 

(1)  in  esophoric  cases , 238 

(2)  in  exophoric  cases 240 

Photograph, 

outer  part  taken  with  a  non-astigmatic  lens,  and  the  inner  part  with 
an  astigmatic  lens,  the  one  pasted  over  the  other,  showing  the 

displacement  of  oblique  lines 95 

Photographs, 

of  Jeager  type  showing  the  distortion  caused  by  oblique  astigma- 
tism     92,  93 

of  a  rectangle  showing  distortion  caused  by  oblique  astigmatism, 

84,  85,  S7 
Prisms, 

in  positions  of  rest,  condemned  in  most  cases,  indorsed  in  some.   189,  213 
Refraction, 

the  work  of,  rmrdriatics  in , 230 

objective  examinations  in, 

(1 )  with  the  ophthalmoscope -31 

(2)  with  the  skiascope 231 

(3)  with  the  ophthalmometer 232 

subjective  examinations  in,  (1)  with  test  lenses 233 

(2)  with  the  Jackson  sphero-cylinder 233 

Retinae, 

corresponding  parts  of 31,  1S9 

images  of  a  retangle  on  the,  in  oblique  astigmatism,  illustrated .      33 

images  of  a  rectangle  on,  non-oblique  astigmatism,  illustrated 2S 

images  of  a  rectangle  on,  in  oblique  astigmatism,  how  fused,  illus- 
trated   , 36 

Reply  to  Dr.  Hotz's  Criticism 63 

Squint, 

internal,  some  of  the  causes  of,  and  how  to  treat 132 

increased  temporarily  by  a  mydriatic 131,  134 

why  this  increase  passes  away 131 

Vision, 

monocular,  the  law  of  direction  unalterable  in 32,  187 

binocular,  the  law  of  corresponding  points  supreme  in 35,  9S 

Wilson  and  His  Camera Si 


The  Ophthalmic  Record. 


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